OK    TIIK 

itrmitu   of 


Division 


Rccci  red 


University  of  California. 


W 


Vl-C- 

L    <^tox*-tw 


LESSONS 


IN 


ELEMENTARY  CHEMISTRY 


INORGANIC   AND   ORGANIC. 


BY 

HENRY   E.   ROSCOE,   B.A.   F.R.S. 

PROFESSOR   OF  CHEMISTRY   IN   OWENS  COLLEGE,    MANCHESTER. 

L  I  |{  II  A  II  * 

r x j VKUSH  v  op 
A  LI  F(  m:\IA. 

NEW   YORK: 

WM.  WOOD  &  CO.,   PUBLISHERS, 
6 1  WALKER  ST. 

1868. 


THE  NEW  YORK  PRINTING  COMPANY, 
81,  83,  and  85  Centre  Street, 
NEW  YORK. 


TABLE   OF    CONTENTS. 


LESSON  PAGE 

I.  INTRODUCTION i 

II.  OXYGEN  AND  HYDROGEN 9 

III.  PHYSICAL  PROPERTIES  OF  GASES,   THERMOME 

TER,    ETC iS 

IV.  CHEMICAL  COMPOUNDS  OF  OXYGEN   AND    HY 

DROGEN—COMPOSITION    AND    PROPERTIES    OF 

WATER 28 

V.  NITROGEN  AND  THE  ATMOSPHERE 42 

VI.  COMPOUNDS  OF  NITROGEN  AND  OXYGEN — DAL- 

TON'S  ATOMIC  THEORY — NITRIC  ACID   ...  50 

VII.  NITROUS  OXIDE — NITRIC  OXIDE — AMMONIA  .    .  57 

VIII.  CARBON — CARBONIC  DIOXIDE 65 

IX.  CARBONIC  OXIDE — COAL  GAS — FLAME  ....  75 
X.  CHLORINE — HYDROCHLORIC    ACID — BLEACHING 

POWDER 85 

XL  BROMINE — IODINE — FLUORINE 95 

XII.  SULPHUR — SULPHURIC  DIOXIDE 102 

XIII.  SULPHURIC  TRIOXIDE — SULPHURIC  ACID  .    .    .  108 

XIV.  SELENIUM — TELLURIUM — SILICON — BORON    .    .  117 
XV.  PHOSPHORUS  AND  ITS  COMPOUNDS 125 

XVI.  ARSENIC — ATOMICITY  OF  THE  ELEMENTS  ...  133 

XVII.  THE  METALLIC 'ELEMENTS — INTRODUCTION   .    .  140 

XVIII.  THE  PRINCIPLES  OF  CRYSTALLOGRAPHY    ...  149 
XIX.  METALS  OF  THE  ALKALIES — POTASH,  SODA  .    .  155 

XX.  METALS     OF    THE    ALKALINE     EARTHS,    AND 

EARTHS — GLASS — PORCELAIN 168 

XXL  MAGNESIUM — ZINC — CADMIUM — MANGANESE      .  177 

XXII.  IRON  AND  ITS  MANUFACTURE 184 

XXIII.  COBALT — NICKEL— CHROMIUM — TIN 191 

XXIV.  ARSENIC — ANTIMONY — LEAD 199 

XXV.  SILVER — COPPER — MERCURY — PLATINUM  .    .    .  207 


vi  Contents. 

LESSON  PAGB 

XXVI.  PRINCIPLES  OF  SPECTRUM  ANALYSIS  AND  SOLAR 

CHEMISTRY 219 

XXVII.  ORGANIC  CHEMISTRY— INTRODUCTION  ....  227 
XXVIII.  DETERMINATION  OF  THE  COMPOSITION  OF  CAR 
BON  COMPOUNDS 236 

XXIX.  THE  MONATOMIC  ALCOHOLIC  GROUP    ....  246 

XXX.  DICARBON,  OR  ETHYL  SERIES 253 

XXXI.  ORGANIC  AMMONIAS 264 

XXXII.  GROUP  OF  FATTY  ACIDS 270 

XXXIII.  DIATOMIC  ALCOHOLS  AND  DERIVATIVES   ...  280 

XXXIV.  DIATOMIC  ACIDS  AND  DERIVATIVES 286 

XXXV.  CYANOGEN  COMPOUNDS 295 

XXXVI.  TRIATOMIC  ALCOHOLS  AND  THEIR  DERIVATIVES  301 

XXXVII.  SACCHARINE  AND  AMYLACEOUS  BODIES     ...  308 

XXXVIII.  GUMS  AND  GLUCOSIDES 315 

XXXIX.  THE  GROUP  OF  AROMATIC  COMPOUNDS     .    .    .  319 
XL.  TURPENTINES,  VEGETABLE  ALKALOIDS  ....  328 
XLI.  ALBUMINOUS  SUBSTANCES — ANIMAL  AND  VEGE 
TABLE  CHEMISTRY 338 

QUESTIONS  AND  EXERCISES 349 

INDEX 375 


I      1     I  »    I  »     \     : 
LI    I>    It  A    it    \ 

rxi  v  I;KSIT  Y  OF 

! 

<  Al  JFOUNIA 

PREFACE. 


IN  the  following  pages  I  have  endeavored  to  arrange 
the  most  important  facts  and  principles  of  Modern 
Chemistry  in  a  plain  but  precise  and  scientific  form, 
suited  to  the  present  requirements  of  elementary 
instruction. 

For  the  purpose  of  facilitating  the  attainment  of 
that  exactitude  in  the  knowledge  of  the  subject, 
without  which  the  introduction  of  physical  science 
into  the  school  system  is  worse  than  useless,  I  have 
added  a  series  of  Exercises  and  Questions  upon  the 
Lessons.  The  pupil  must  learn  to  work  out  accu 
rately  both  the  numerical  and  descriptive  examples, 
and  the  teacher  may  find  it  advisable  to  add  large 
ly  to  their  number.  Particular  attention  should  be 
given  to  the  calculation  of  the  relations  between 
the  weights  of  gases,  and  their  volumes  measured 
under  varying  circumstances  of  temperature  and 
pressure. 

The  metric  system  of  weights  and  measures,  and 
the  centigrade  thermometric  scale,  are  used  through 
out  the  work. 


viii  Preface. 

I  have  much  pleasure  in  thanking  my  friend  atid 
assistant,  Mr.  Schorlemmer,  for  the  aid  which  he 
has  given  me,  especially  in  revising  the  proofs  ;  and 
I  have  also  to  acknowledge  the  care  and  attention 
bestowed  on  the  woodcuts  by  Mr.  Dickes. 

H.  E.  R. 

MANCHESTER. 


For  further  information  concerning  the  absolute 
weights  of  the  gases  than  is  given  on  p.  26,  a  para 
graph  in  the  Appendix,  page  373,  may  be  con 
sulted. 


i,'   i 


CALIFORNIA. 


LESSON  I. 

BY  chemical  action  we  signify  that  which  occurs  when  two  or 
more  substances  so  act  upon  another  as  to  produce  a  third 
substance  differing  altogether  from  the  original  ones  in  pro 
perties  ;  or  when  one  substance  is  brought  under  such  con 
ditions  that  it  forms  two  or  more  bodies  differing  from  the 
original  one  in  properties.  Thus,  if  powdered  sulphur  and 
fine  copper  filings  be  well  mixed  together,  the  color  of  the 
sulphur  as  well  as  that  of  the  copper  will  disappear,  and  to 
the  unaided  eye  the  mixture  presents  a  uniform  greenish  tint ; 
by  the  help  of  the  microscope,  however,  the  particles  of  cop 
per  maybe  seen  lying  by  the  side  of  the  particles  of  sulphur  ; 
and  we  can  wash  away  the  lighter  sulphur  with  water,  leaving 
the  heavier  copper  behind.  Here  no  chemical  action  has 
occurred  ;  the  sulphur  and  copper  were  only  mechanically 
mixed.  If  we  next  gently  heat  some  of  the  mixture  we  see 
that  it  soon  begins  to  glow,  and  on  examining  the  mass  we 
notice  that  both  the  copper  and  the  sulphur  have  disappeared 
as  such,  that  they  cannot  be  distinguished  even  by  the  most 
powerful  microscope,  and  that  in  their  place  we  have  formed 
a  black  substance  possessing  properties  entirely  different 
from  those  possessed  either  by  the  copper  or  by  the  sulphur. 
Here  a  chemical  change  has  occurred  ;  the  copper  and  the 
sulphur  are  said  to  have  combined  chemically  to  form  ^com 
pound,  out  of  which  these  two  substances  can  be  regained  in. 
exactly  the  quantities  used.  In  like  manner  when  a  candle 
burns  in  the  air  a  chemical  change  is  going  on ;  and  although 
the  candle  gradually  disappears,  the  materials  of  which  it  is 
made  up  are  not  destroyed  or  lost ;  they  simply  pass  into  a 


2  Elementary  Chemistry* 

state  in  which  they  are  invisible  to  our  eyes,  but  their  pres 
ence  may  be  ascertained  by  other  means.  Thus,  if  we  burn 
a  candle  for  a  few  minutes  in  a  clean  bottle  filled  with  air,  and 
afterwards  pour  in  some  clear  lime-water,  we  shall  notice  that 
the  liquid,  which  remains  clear  in  pure  air,  becomes  at  once 
milky,  showing  the  presence  of  an  invisible  gaseous  body 
produced  by  the  burning  of  the  candle,  which  possesses  pro 
perties  different  from  those  of  pure  air.  Although  an  ap 
parent  loss  of  matter  occurs  when  a  candle  burns,  it  is  easy 
to  show  by  a  simple  experiment  not  only  that  this  is  not  the 
case,  but  that  on  the  contrary  an  increase  of  weight  has  oc 
curred  ;  this  increase  is  occasioned  by  the  constituent  parts 
of  the  tallow  or  wax  having  united  chemically  with  an  invisible 
gas  (called  oxygen)  present  in  the  air.  For  this  purpose  a 
piece  of  glass  tubing  |-  inch  wide,  and  10  inches  long,  is  closed 
at  each  end  with  a  cork  ;  through  the  upper  cork  a  bent  glass 
tube  passes,  whilst  through  the  lower  one  several  holes  are 
bored,  and  into  one  of  these  a  small  taper  is  fastened.  The 
upper  half  of  the  tube  is  filled  with  pieces  of  caustic  soda,  a 
grid  of  perforated  zinc  being  fixed  inside  the  tube  to  keep 
them  in  their  place.  The  tube  thus  arranged  is  hung  at  the 
end  of  one  arm  of  a  pair  of  scales,  and  exactly  counterpoised 
by  weights  placed  in  the  pan  on  the  other  arm.  The  top  of 
the  tube  is  now  connected,  by  means  of  a  piece  of  vulcanised 
caoutchouc  tubing,  with  a  closed  vessel  filled  with  water  and 
furnished  with  a  stop-cock  through  which  the  water  can  flow 
out ;  on  opening  this  stop-cock,  as  the  water  flows  out,  air 
passes  in  to  supply  its  place,  through  the  holes  in  the  per 
forated  cork.  This  cork  is  then  removed,  the  taper  lighted, 
and  the  cork  and  taper  quickly  replaced  ;  after  the  candle  has 
burnt  for  three  or  four  minutes,  the  vulcanised  tubing  is  dis 
connected,  and  the  glass  tube  allowed  to  hang  freely.  It  is 
then  seen  that  the  weight  of  the  tube  is  greater  than  it  was 
before  the  candle  was  burnt,  the  pieces  of  caustic  soda  having 
absorbed  the  substances  (carbonic  acid  and  water)  produced 
by  the  combination  of  the  constituents  of  the  taper  (carbon 
and  hydrogen)  with  the  oxygen  of  the  air. 


Elementary  Chemistry. 


By  the  careful  examination  of  all  the  known  cases  of  chem 
ical  action  it  has  been  satisfactorily  proved  that  a  loss  of  matter 
never  takes  place,  that  matter  is  indest?'uctible,  and  that  in 
chemical  actions  such  as  that  going  on  in  the  burning  of  the 
candle,  a  change  of  state  and  not  an  annihilation  of  matter 
occurs.  The  truth  of  this  first  great  principle  in  chemical 
science  has  been  gradually  demonstrated  by  finding  that  the 
weights  of  the  substance  acting  chemically  upon  one  another, 
always  remain  the  same  after  as  before  the  chemical  changes 
have  occurred.  For  determining  very  accurately  the  weight 


FIG.  i. 

of  substances,  an  instrument  called  the  chemical  balance  is 
employed.  Fig.  I  represents  one  form  of  chemical  balance. 
It  consists  of  a  perforated  brass  beam  (A  A)  vibrating  about 
its  centre,  at  which  is  fixed  a  triangular  knife-edge  of  agate 
(C):  this  rests  upon  a  horizontal  agate  plane  attached  to  the 
upright  brass  pillar.  To  each  end  of  the  beam  the  light  brass 
pans  (BB)  are  attached,  each  pan  hanging  on  by  an  agate 
knife-edge  to  an  agate  plane  fixed  on  the  end  of  the  beam  at 
(D  D).  This  mode  of  rest  and  support  is  to  render  the  amount 
of  friction  as  small  as  possible,  and  thus  to  insure  delicacy  in 


4  Elementary  CJiemistry. 

the  instrument.  In  order  to  prevent  the  agate  edges  from 
being  spoilt  by  constant  wear  on  the  agate  planes,  the  beam 
and  the  ends  (D  D)  are  supported  by  the  brass  arm  (E  E)  when 
the  balance  is  not  in  use,  so  that  the  agate  surfaces  do  not 
touch ;  the  beam  and  pans  are  released  when  required  by 
turning  the  handle  (F).  The  body  to  be  weighed  is  placed  in 
one  pan,  and  weights  added  one  by  one  to  the  other  until  the 
instrument  is  in  equilibrium ;  this  is  ascertained  by  the  long 
pointer  (G)  vibrating  to  an  equal  distance  on  each  side  of  the 
central  mark.  A  balance  such  as  that  represented  in  the 
figure  will  turn  with  Vi7  of  a  milligramme  when  loaded  with 
100  grammes  (see  p.  21  ),  or  will  indicate  the  one-millionth 
part  of  the  substance  weighed. 

The  aim  of  the  chemist  is  to  examine  the  properties  of  all 
substances  with  regard  to  their  actions  upon  one  another  in 
producing  bodies  essentially  differing  from  the  originals.  In 
order  thoroughly  to  carry  out  his  purpose  he  is  obliged  to 
resort  to  experiment,  that  is,  he  has  to  place  the  substances 
which  he  is  examining  under  circumstances,  perhaps  not 
found  in  nature,  which  he  can  control  and  vary.  Hence 
chemistry  is  called  an  experimental  science.  In  thus  in 
vestigating  all  the  materials  within  his  reach,  whether  solid, 
liquid,  or  gaseous,  whether  contained  in  the  earth,  sea,  or  air, 
whether  belonging  to  the  animal  or  to  the  vegetable  creation, 
the  chemist  finds  himself  obliged  to  divide  substances  into 
two  great  classes  :  (i)  those  which  he  is  able  to  split  up  into 
two  or  more  essentially  different  substances,  and  (2)  those 
which  he  is  unable  thus  to  split  up,  and  out  of  which  nothing 
essentially  different  from  the  original  substances  has  been 
obtained.  To  the  first  class  the  name  of  compound,  to  the 
second  the  name  of  elementary  or  simple  substances  has  been 
given.  Compound  bodies  are  made  up  of  two  or  more  ele 
mentary  substances  chemically  combined  with  each  other: 
thus  sulphur  and  copper  are  elementary  bodies — out  of  each 
of  these  nothing  different  from  sulphur  or  copper  can  be  ob 
tained  ;  whereas,  when  the  two  bodies  are  heated  together,  a 
compound  is  formed  from  which  both  of  the  original  element- 


Elementary  Chemistry.  5 

ary  constituents  can  at  any  time  bo  prepared.  Water  is  a 
compound  body,  it  can  be  split  up  into  two  elementary  gases, 
hydrogen  and  oxygen  ;  common  salt,  again,  is  a  compound  of 
a  gas  (chlorine)  with  a  metal  (sodium) ;  and  limestone,  clay, 
sugar,  and  wax  may  serve  as  examples  of  compound  bodies  : 
whilst  phosphorus,  charcoal,  iron,  mercury,  and  gold  may  be 
mentioned  as  belonging  to  the  class  of  simple  substances. 
The  following  experiment  well  illustrates  the  decomposition 
of  a  compound  into  two  simple  substances.  A  small  quantity 
of  the  red  powder  called  mercuric  oxide,  is  introduced  into  a 
test  tube  and  heated  in  a  gas  flame  ;  when  hot,  the  oxide 
gradually  decomposes,  a  grey  deposit  of  metallic  mercury  in 
small  globules  collects  upon  the  cooler  parts  of  the  glass, 
whilst  the  tube  becomes  filled  with  colorless  oxygen  gas 
whose  presence  can  be  demonstrated  by  the  rekindling  of  a 
glowing  chip  of  wood  plunged  into  the  tube.  On  continuing 
the  heat,  the  whole  of  the  red  powder  is  found  to  be  split 
up  into  the  two  elements,  mercury  and  oxygen,  which  together 
weigh  exactly  as  much  as  the  red  oxide  from  which  they  were 
obtained. 

The  elementary  bodies,  for  the  sake  of  convenience,  are 
arbitrarily  divided  into  two  classes,  the  metals  and  the  non- 
metals.  In  the  first  are  placed  elements  such  as  gold,  iron, 
lead,  mercury,  tin  ;  in  the  second,  those  elements  which  are 
gases  at  the  ordinary  temperature,  such  as  oxygen,  hydrogen, 
&c.,  together  with  some  solid  elements,  as  sulphur,  charcoal, &c. 
The  number  of  the  metals  is  much  larger  than  that  of 
the  non-metals  ;  we  are  acquainted  with  forty-nine  metals, 
and  with  only  fourteen  non-metals.  These  sixty-three  ele 
ments  constitute  the  material  out  of  which  the  whole  fabric  of 
the  science  is  built ;  every  description  of  matter  which  has  been 
examined  is  made  up  of  these  elements,  either  combined  to 
gether  to  form  compounds,  or  in  the  uncombined  or  free  state. 
The  science  of  chemistry  has  for  its  aim  the  experimental 
examination  of  the  properties  of  the  elements  and  their  com 
pounds,  and  the  investigation  of  the  laws  which  regulate  their 
combination  one  with  another.  The  applications  of  the  prin- 


6  Elementary  Chemistry. 

ciples  of  chemical  science  to  the  arts  and  manufactures  are 
of  the  highest  importance  and  interest ;  they  have  exerted  a 
most  material  influence  upon  the  progress  of  civilization,  and 
have  greatly  tended  to  the  elevation  and  benefit  of  mankind  ; 
the  instances  are  innumerable  in  which  altogether  new 
branches  of  industry  have  sprung  up  from  the  happy  applica 
tion  of  simple  chemical  principles,  and  there  is  scarcely  an 
article  in  common  use  in  the  production  of  which  some  appli 
cation  of  chemistry  has  not  proved  of  essential  value. 

The  following  is  a  complete  list  of  the  elementary  bodies 
known  at  present  (1866).  The  names  printed  in  large  capitals, 
as  BORON,  are  the  non-metals,  those  in  small  capitals,  as 
ALUMINIUM,  are  the  more  commonly  occurring  metals,  those 
in  small  type,  as  Cadmium,  are  the  rarer  metals  : 

Names.  Symbols.  Combining  Weight. 

ALUMINIUM Al 27-4 

ANTIMONY Sb 122     • 

ARSENIC  ......  As 75 

BARIUM Ba 137 

BISMUTH Bi 210 

BORON  .     .    .    .    ,     .  B ii 

BROMINE     %•    ..-i     .  Br 80 

Cadmium       Cd 112 

Caesium    .......  Cs 133 

CALCIUM Ca 40 

CARBON C 12 

CHLORINE    .     .     .     .  Cl 35-5 

Cerium Ce 92 

CHROMIUM Cr 52-5 

COBALT    ......  Co  587 

COPPER Cu 63-5 

Didymium D 96 

Erbium E 

FLUORINE     .     .     .     .  F 19 

Glucinum Gl 9'3 

GOLD        Au 197 


Elementary  Chemistry.  J 

Names.  Symbols.  Combining  Weight. 

HYDROGEN  .     .     .     .  H     ......         i 

Indium      ......  In    ......  74 

IODINE  ......  I      ......  127 

Iridium     ......  Ir    ......  198 

IRON     .......  Fe  ......  56 

Lanthanum    .     .     .     .     :  La  ......  92 

LEAD    .......  Pb  ......  207 

Lithium     ......  Li    ......         7 

MAGNESIUM  .....  Mg  ......       24 

MANGANESE     ....  Mn  ......       55 

MERCURY      .....  Hg  ......  200 

Molybdenum      ....  Mo  ......       96 

NICKEL    ......  Ni   ......      58<7 

Niobium    ......  Nb  ......       94-0 

NITROGEN    .     .     .     .  N     ......       14 

Osmium     ......  Os  ......  199-2 

OXYGEN     :    .J  ,  f.  ft  ?>  -A-    I-.  •-.-•     -       l6 
f 


Palladium      .     .     .     .  :\  V    .     .     .  106-6 

PHOSPHORUS  .     .     .  P     ......  31 

PLATINUM    I    '>  /  \   (•  ^f-.l  T  V  .(»:  i97'S 

POTASSIUM   .....  K    ......  39'i 

Rhodium.     •  CALll^li-Sf  I  -A'     '  I04'4 

Rubidium      .....  Rb  .     .     .     .     .'  /    85-4 

Ruthenium     .....  Ru  .....  '    .  104-4 

SELENIUM     .     .     .     .  Se  ......  79'5 

SILVER      ......  Ag  ......  108 

SILICON     .....  Si    ......       28 

SODIUM     ......  Na  ......      23 

STRONTIUM  .....  Sr    ......      87-5 

SULPHUR  .....  S     ......      32 

Tantalum       .....  Ta  ......  172-0 

TELLURIUM.     .     .     .  Te  ......  129 

Thallium  ......  Tl    ......  204 

Thorium    ......  Th  ......  1157 

TIN  ........  Sn  ......  118 

Titanium  ......  Ti   .....            5° 


8  Elementary  Chemistry. 

Names.  Symbols.  Combining  Weight 

Tungsten W 184 

Uranium U 120 

Vanadium V 137 

Yttrium Y 

ZINC Zn 65*2 

Zirconium Zr 89-6 

Some  of  these  are  very  abundant  and  occur  widely  dis 
tributed,  whilst  others  have  only  been  found  in  such  minute 
quantities,  and  in  such  rare  fragments,  that  their  properties 
have  not  yet  been  satisfactorily  examined.  Thus,  for  instance, 
oxygen  occurs  throughout  the  air,  sea,  and  solid  earth,  in  such 
quantities  as  to  make  up  nearly  half  the  weight  of  our  planet. 
Whereas  the  metals  yttrium,  erbium,  indium,  &c.  have  only 
as  yet  been  met  with  in  most  minute  quantities. 

The  elements  are  distributed  very  irregularly  throughout 
our  planet :  only  four  occur  in  the  air,  some  thirty  have  been 
found  in  the  sea;  whilst  all  the  known  elements  occur  vari 
ously  dispersed  in  the  solid  mass  of  the  earth.  The  following 
table,  giving  the  composition  by  weight  of  the  primary  rocks, 
shows  that  the  bulk  of  the  earth's  solid  body  is  made  up  of 
only  eight  elements,  the  remainder  being  found  in  much 
smaller  quantities  : 

Composition  of  the  Earth's  Solid  Crust  in  100  parts  by  weight. 

Calcium  ....  6'6  to  0-9 

Magnesium       .     .  27  ,.  OT 

Sodium   ....  2'4  ,,  2-5 

Potassium    ...  1-7  „  3-1 

Doubtless  other  elements  exist  undiscovered  in  the  earth 
in  addition  to  the  sixty-four  now  known,  for  we  find  that 
where,  with  the  progress  of  science,  new  and  more  accurate 
methods  of  examining  the  composition  of  matter  have  been 
employed,  the  existence  of  new  elements  has  frequently  been 
brought  to  light;  thus  within  the  last  four  years,  no  less  than 
four  new  elements  have  been  discovered  by  the  help  of  the 
new  method  of  spectrum  analysis  (see  p.  219).  Whether  any 


Oxygen    .     .     .  44-0  to  487 

Silicon      .     .     .  22-8  „  36*2 

Aluminium  .     .  9*9  ,,     6-i 

Iron     ....  9.9  „     2-4 


Elementary  Chemistry.  9 

of  the  bodies  now  termed  elementary  may,  by  the  application 
of  more  powerful  means  than  we  at  present  possess,  at  some 
future  time  be  split  up  into  simpler  constituents,  is  a  question 
which  we  cannot  answer  with  certainty.  Judging,  however, 
from  precedent,  we  may  consider  the  occurrence  of  such  a 
thing  as  possible,  or  even  likely ;  for  the  alkalies  potash  and 
'soda  were  believed  to  be  elements  until  the  year  1808,  when 
Sir  H.  Davy  proved  that  they  were  in  reality  compounds. 

Our  knowledge  of  the  chemical  composition  of  the  heavenly 
bodies  was  restricted,  until  lately,  to  that  gained  from  the 
examination  of  meteorites,  in  which  no  element  has  been 
found  which  is  not  known  in  the  earth.  Within  the  last  few 
years  the  foundations  of  a  solar  and  stellar  chemistry  have, 
however,  been  laid  ;  and  we  are  now  able  to  ascertain  the 
presence  of  many  well-known  chemical  substances  in  the  sun 
and  far  distant  fixed  stars  with  as  great  exactitude  and  certainty 
as  we  are  able  to  prove  their  presence  in  terrestrial  matter 
(see  p.  223). 


NON-METALLIC  ELEMENTS. 

LESSON   II. 

Oxygen.  Symbol  O.  Combining  Proportion  16.  Density  16. 
OXYGEN  is  a  colorless  invisible  gas,  possessing  neither  taste 
nor  smell.  It  exists  in  the  free  state  in  the  atmosphere,  of 
which  it  constitutes  about  one-fifth  by  bulk,  whilst  in  com 
bination  with  the  other  elements,  it  forms  nearly  half  the 
weight  of  the  solid  earth,  and  eight-ninths  by  weight  of  water. 
Oxygen  was  discovered  in  the  year  1774  by  Priestley,  and  in 
dependently  in  1775  by  Scheele.  Lavoisier  first  clearly  pointed 
out  in  1778  the  part  played  by  oxygen,  and  explained  the 
chemical  changes  that  go  on  when  bodies  burn  in  the  air. 
The  birth  of  the  modern  science  of  chemistry  may  be  dated 
from  the  discovery  of  oxygen.  Oxygen  gas  can  be  prepared 
from  the  air,  but  it  is  more  easily  obtained  from  many  com 
pounds  which  contain  it  in  large  quantities.  Priestley  prepared 

i* 


IO  Elementary  Chemistry. 

oxygen  by  heating  red  mercuric  oxide  :  this  substance  is 
made  up  of  200  parts  by  weight  of  mercury,  and  sixteen  parts 
of  oxygen  ;  when  strongly  heated,  it  is  decomposed,  yielding 
metallic  mercury  and  oxygen  gas.  Oxygen  can  be  more 
cheaply  obtained  by  heating  potassium  chlorate  (commonly 
called  chlorate  of  potash),  a  white  salt  which  yields  on  heating 
39'2  per  cent,  of  its  weight  of  this  gas.  In  order  to  collect 
the  oxygen  thus  given  off,  powdered  potassium  chlorate  is 
placed  in  a  small  thin  glass  flask,  furnished  with  a  well-fitting 
cork,  into  which  a  bent  tube  is  inserted.  The  lower  end  of 
the  tube  dips  under  the  surface  of  water  in  a  pneumatic 
trough,  and  the  gas,  on  being  evolved,  bubbles  out  from  the 
end  of  the  tube,  and  is  collected  in  jars  or  bottles  filled  with 
water,  and  placed  with  their  mouths  downwards  in  the  trough. 
Fig.  2  shows  the  arrangement  of  the  apparatus  needed  for 


FIG.  3. 

the  preparation  of  oxygen  gas.  If  a  small  quantity  of  manga 
nese  di-oxide  (black  oxide  of  manganese)  be  mixed  with  the 
potassium  chlorate,  the  oxygen  is  given  off  from  the  chlorate 
at  a  much  lower  temperature,  and  thus  the  evolution  of  the 
gas  is  facilitated,  but  the  manganese  di-oxide  undergoes  no 
change  whatever.  All  the  elements,  with  the  single  exception 
of  fluorine,  combine  with  oxygen  to  form  oxides.  In  this  act 
of  combination,  which  is  termed  oxidation,  heat  is  always, 
and  light  is  frequently,  given  off.  When  bodies  unite 
with  oxygen,  evolving  light  and  heat,  they  are  said  to 
burn,  or  undergo  combustion.  All  bodies  which  burn  in  the 
air,  burn  with  increased  brilliancy  in  oxygen  gas  ;  and  many 
substances  such  as  iron,  which  do  not  readily  burn  in  the  air, 


*  Elementary  Chemistry.  1 1 

may  be  made  to  do  so  in  oxygen.  A  red-hot  chip  of  wood, 
or  a  taper  with  glowing  wick,  is  suddenly  rekindled  and  bursts 
into  flame  when  plunged  into  a  jar  of  this  gas.  Sulphur, 
which  in  the  air  burns  with  a  pale  lambent  flame,  emits  in 
oxygen  a  bright  violet  light ;  and  a  small  piece  of  phosphorus, 
when  inflamed  and  placed  in  oxygen,  burns  with  a  dazzling 
light.  If  the  jars,  in  which  these  experiments  have  been  per 
formed,  be  afterwards  examined,  it  is  found  that  the*  sub 
stances  produced  by  combustion  in  oxygen  possess  acid  char 
acters  ;  they  have  the  power  of  turning  red  certain  vegetable 
blue  coloring  matters,  such  as  litmus  :  owing  to  this  fact,  La 
voisier  gave  to  oxygen  the  name  it  bears  (from  651;?,  acid,  y? n/aw,. 
I  produce).  Fine  iron  wire  can  be  easily  burnt  in  oxygen  by 
tipping  the  end  with  burning  sulphur,  and  then  plunging  the 
iron  thus  tipped  into  a  jar  of  the  gas  ;  the  oxide  of  iron,  formed 
by  the  combustion,  drops  down  in  the  molten  state. 

Many  other  substances  may  be  employed  for  the  prepara 
tion  of  oxygen  ;  thus,  if  large  quantities  of  the  gas  are  needed, 
manganese  di-oxide  (a  substance  of  frequent  occurrence  in 
nature)  may  be  heated  to  redness  in  an  iron  bottle  ;  100  parts 
by  weight  of  the  oxide  yield  12-3  by  weight  of  oxygen. 
Another  interesting  decomposition  by  which  oxygen  is  set 
free,  is  that  effected  by  sunlight  upon  the  carbonic  acid  gas 
contained  in  the  air  ;  this  is  accomplished  by  the  green  color 
ing  matter  of  plants.  Sunlight  has  the  power,  in  presence  of 
this  green  coloring  matter,  of  decomposing  carbonic  acid  ;  the 
carbon  is  taken  up  by  the  plant  for  its  growth,  whilst  the 
oxygen  is  set  free,  and  is  afterwards  used  by  animals  for  the 
support  of  the  process  of  respiration.  In  the  act  of  inspiration 
(filling  the  lungs)  animals  breathe  in  the  oxygen  of  the  air, 
whilst  in  that  of  expiration  (emptying  the  lungs)  they 
breathe  out  carbonic  acid  gas.  Hence  oxygen  is  neces 
sary  to  animal  life,  wherefore  this  gas  was  formerly  termed 
vital  air.  The  chemical  change  which  oxygen  effects  upon 
the  body  of  the  animal  is  in  fact  identical  with  that  which 
goes  on  when  a  piece  of  charcoal  burns  in  the  air  or  oxygen  ; 
this  may  be  rendered  evident  by  a  simple  experiment.  If 


12  Elementary  Chemistry. 

some  clear  limewater  be  poured  into  a  bottle  of  oxygen  in 
which  charcoal  has  been  burnt,  the  limewater  will  become 
milky,  owing  to  the  formation  of  a  compound  of  lime  and 
carbonic  acid  (called  chalk),  this  acid  being  produced  by  the 
combustion ;  if  the  air  contained  in  the  lungs  be  next  blown 
through  a  piece  of  glass  tubing  into  some  more  clear  lime- 
water,  a  turbidity  (from  the  formation  of  chalk)  will  at  once 
occur,  proving  that  carbonic  acid  gas  is  given  off  from  the 
lungs.  This  carbonic  acid  arises  from  the  oxidation  of  the 
constituents  of  the  body,  and  by  this  oxidation  the  heat  of  the 
body,  which  is  greater  than  that  of  surrounding  inanimate 
objects,  is  sustained.  When  this  chemical  process  stops,  the 
animal  dies,  and  the  temperature  of  the  body  sinks  to  that  of 
the  neighboring  objects.  Carbonic  acid,  nitrogen,  and  some 
other  gases  cause  death  when  inhaled,  because  they  do  not 
contain  free  oxygen,  and  hence  the  process  of  oxidation  in 
the  body  ceases.  This  cause  of  death  is  independent  of  any 
poisonous  action  of  the  gases.  Other  processes  for  preparing 
oxygen  on  a  large  scale  will  be  mentioned  in  the  lessons  relat 
ing  to  bleaching  powder,  sulphuric  acid,  and  barium  peroxide. 
When  the  composition  of  a  substance  is  determined  by 
splitting  the  compound  into  its  elementary  constituents,  a 
chemical  analysis  of  that  substance  is  said  to  have  been 
made  :  when  the  composition  is  ascertained  by  bringing  the  con 
stituent  parts  together,  we  are  said  to  determine  the  composi 
tion  by  synthesis.  If  we  analyze  potassium  chlorate  we  find 
that,  from  whatever  source  this  salt  may  be  derived,  it  always 
possesses  the  same  unalterable  composition.  This  is  true  of 
every  definite  chemical  compound ;  indeed,  were  it  not  so,  chem 
istry  as  a  science  could  not  exist.  Potassium  chlorate  is  made 
up  of  three  elementary  bodies,  chlorine,  potassium,  and  oxy 
gen  combined  together  in  the  following  proportions  by  weight  :- 

Chlorine  .     .     .     35^5  parts  by  weight. 

Potassium     .     .     39-1  " 

Oxygen    ...     48*0  " 

Potassium  Chlorate     .    122-6  " 


Elementary  Chemistry.  13 

When  this  salt  is  heated,  the  whole  of  the  oxygen  comes 
off  as  gas  :  122-6  parts  yield  48  parts  of  oxygen,  while  74-6 
parts  of  a  white  solid  compound  of  chlorine  and  potassium, 
called  potassium  chloride,  remain  behind.  Hence  the  weight 
of  oxygen  which  can  be  obtained  from  any  given  weight  of 
potassium  chlorate,  and  vice  versa,  can  be  calculated.  In 
order  to  express  the  composition  of  substances  more  con 
veniently  than  can  be  done  by  writing  the  names  of  the 
elementary  constituents  at  full  length,  chemists  use  a  kind 
of  short-hand,  or  symbolic  language,  some  of  the  princi 
ples  of  which  must  now  be  shortly  explained.  Instead  of 
writing  the  whole  name,  the  first  letter  or  the  first  two  letters 
of  the  name  alone  are  employed  to  designate  the  element ; 
sometimes  using  the  English,  sometimes  the  Latin  or  Greek 
name.  Thus  Cl  stands  for  Chlorine,  O  for  Oxygen,  and  K 
(from  Kali,  another  name  for  Potash)  for  Potassium. 

These  letters,  however,  signify  more  than  this  :  they  stand 
not  only  for  the  elements  in  question,  but  they  all  have  certain 
numbers  belonging  to  them  which  indicate  the  proportions  by 
weight  in  which  the  several  elements  combine  with  each  other. 
Thus  Cl  does  not  signify  any  weight  of  chlorine,  but  always 
exactly  35-5  parts  by  weight ;  K  does  not  signify  any  weight 
of  Potassium,  but  always  39-1  parts  ;  while  O  signifies  always 
16  parts  by  weight  of  Oxygen.  Hence  it  is  evident  that  we 
may  express  not  only  the  qualitative  but  also  the  quantita 
tive  chemical  composition  of  potassium  chlorate  by  the  sym 
bol  KC1O3,  in  which  O3  means  3x16  parts  of  Oxygen.  In 
like  manner  each  of  the  64  elements  has  its  particular  symbol 
and  number  attached,  signifying  the  proportion  by  weight  in 
which  it  combines  (see  Table,  page  6).  The  reasons  which 
have  led  Chemists  to  adopt  these  special  •numbers  for  the 
combining  weights  or  proportions  of  the  elements,  and  the 
laws  which  have  been  found  to  regulate  their  combination, 
will  be  explained  as  our  stock  of  chemical  facts  gradually 
becomes  larger. 

The  density  or  weight  of  a  given  volume  of  oxygen,  com 
pared  with  that  of  the  same  volume  of  hydrogen,  is  found  tQ 


14  Elementary  Chemistry. 

be  sixteen,  hydrogen,  as  the  lightest  body  known,  being  taken 
as  the  standard.  The  specific  gravity  of  oxygen,  compared 
with  the  weight  of  the  same  volume  of  air  taken  as  the  unit, 
is  found  to  be  1-1056.  One  litre  of  oxygen  gas  at  o°  C,  and 
under  the  pressure  of  760  millimetres  of  mercury,  weighs 
1-4298  grammes. 

Pure  oxygen  undergoes  a  remarkable  modification  when  a 
series  of  electric  discharges  is  passed  through  the  gas  :  it  thus 
attains  more  active  properties  ;  it  is  able  to  set  free  iodine 
from  potassium  iodide,  and  to  effect  oxidations  which  common 
oxygen  is  unable  to  bring  about.  This  allotropic  modification 
of  oxygen  has  been  termed  Ozone.  If  a  series  of  electric  dis 
charges  be  passed  through  pure  oxygen,  the  gas  becomes 
diminished  in  volume  by  about  one-twelfth,  and  is  partly 
transformed  into  ozone.  If  any  substance  be  present,  such  as 
potassium  iodide,  capable  of  absorbing  the  ozone  as  it  is 
formed,  the  whole  of  the  oxygen  can  be  transformed  into  this 
active  modification.  The  peculiar  smell  which  is  observed 
when  an  electrical  machine  is  worked,  is  caused  by  the 
presence  of  ozone  ;  and  if  a  paper,  dipped  in  a  solution  of 
potassium  iodide  and  starch  paste,  be  held  opposite  a  point  on 
the  conductor  of  the  machine,  the  paper  becomes  blue,  owing 
to  the  liberation  of  iodine  and  the  formation  of  a  blue  com 
pound  of  iodine  and  starch.  Ozone  can  be  obtained  in  several 
other  ways  ;  it  is  formed  when  a  stick  of  phosphorus  is 
allowed  to  hang  in  a  bottle  filled  with  moist  air  ;  it  is  pro 
duced  in  small  quantities  in  the  electrolytic  decomposition  of 
water  (see  p.  32) ;  and  it  is  formed  by  the  action  of  strong 
sulphuric  acid  upon  a  salt  called  potassium  permanganate. 
There  has  been  a  great  deal  of  discussion  respecting  the 
nature  and  composition  of  ozone.  It  appears,  however,  to  be 
proved  that  it  is  simply  oxygen  in  a  condensed  form. 

Hydrogen.     Symbol  H.    Combining  Proportion  I.   Density  I. 

Hydrogen  is  a  colorless  invisible  gas,  possessing  neither 

taste  nor  smell ;  it  is  the  lightest  body  known,  being  14-47 

times  lighter  than  air.     It  occurs  free  in  small  proportions  in 


Elementary  Chemistry.  15 

certain  volcanic  gases,  but  it  is  found  in  much  larger  quanti 
ties,  combined  with  oxygen  to  form  water  (v'6wp,  water,  and 
y£»W«,  I  produce),  and  it  is  by  the  decomposition  of  water,  or 
of  some  other  similar  hydrogen  compound,  that  the  gas  is 
always  prepared.  Hydrogen  appears  to  have  been  first 
obtained  by  Paracelsus  in  the  sixteenth  century,  but  its  pro 
perties  were  first  exactly  studied  by  Cavendish  in  1781.  One- 
ninth  of  the  weight  of  water  consists  of  hydrogen,  and  this  gas 
can  readily  be  obtained  from  it  by  the  action  of  certain  metals, 
which  decompose  the  water,  combining  with  the  oxygen  to 
form  a  metallic  oxide,  and  liberating  the  hydrogen  as  a  gas. 
The  metals  of  the  alkalies,  potassium  and  sodium,  decompose 
water  at  the  ordinary  temperature  of  the  air  ;  some  other 
metals,  as  iron,  are  only  able  to  do  so  at  a  red  heat ;  whilst 
others,  for  instance  silver  and  gold,  are  unable  to  decompose 


*    < : 


water  at  all.  When  a  small  piece  of  potassium  is  thrown 
into  water,  an  instantaneous  decomposition  of  the  water 
ensues,  potassium  oxide  (potash)  is  formed,  and  the  hydrogen 
of  the  water  is  liberated,  so  much  heat  being  at  the  same  time 
evolved,  that  the  hydrogen  takes  fire  and  burns.  If  the  potas 
sium,  or  still  better,  sodium,  be  wrapped  in  a  piece  of  wire 
gauze,  and  thus  held  in  the  water  of  the  pneumatic  trough, 
under  the  mouth  of  a  cylinder,  the  hydrogen  gas  thus  liberated 


i6 


Elementary  Chemistry. 


may  be  collected,  and  its  properties  examined.  To  prepare 
hydrogen  by  the  action  of  red-hot  iron  on  water,  a  wrought 
iron  pipe,  like  a  gun-barrel,  filled  with  iron  turnings,  must  be 
heated  in  a  furnace,  Fig.  3,  and  steam  from  a  small  flask  or 
boiler,  passed  over  the  red-hot  metal  through  the  tube ; 
hydrogen  gas  is  given  off,  and  oxide  of  iron  left  in  the  tube. 
The  most  convenient  process  of  preparing  pure  hydrogen  in 
quantity  depends  upon  a  property  possessed  by  those  metals, 
such  as  iron  or  zinc,  which  decompose  water  at  a  red  heat, 
namely,  that  these  metals  are  able  to  evolve  hydrogen  from 
water  at  the  ordinary  temperature  of  the  air  if  a  dilute  acid  be 
present. "  For  the  purpose  of  thus  obtaining  hydrogen,-a  flask 
or  bottle  is  provided  with  a  cork  and  tube  as  represented  in 
Fig.  4,  some  zinc  clippings  are  introduced,  and  a  mixture  of 


FIG.  4. 

one  part  of  sulphuric  acid  and  eight  parts  of  water  poured  in 
through  the  tube  funnel.  After  a  few  minutes  a  rapid  effer 
vescence  commences,  and  the  evolved  gas  is  collected  over 
water  in  bottles  or  cylinders  as  in  the  case  of  oxygen.  Care 
must,  however,  be  taken  that  all  the  air  is  expelled  from  the 
flask  before  the  hydrogen  is  collected;  this  is  easily  ascer- 


Elementary  Chemistry.  17 

tained  to  be  the  case  by  filling  a  test  tube  with  the  gas,  and 
trying  whether  it  burns  quietly  when  a  lighted  candle  is 
brought  to  the  mouth  of  the  tube  held  downwards.  Hydrogen 
burns  in  the  air  when  a  light  is  brought  to  it  with  a  very 
slightly  luminous,  although  extremely  hot  flame  ;  and  in  the 
process  the  hydrogen  combines  with  the  oxygen  of  the  air, 
forming  water.  The  production  of  water  by  the  combustion 
of  hydrogen  in  the  air  may  easily  be  shown  by  bringing  a 
bright  dry  glass  over  the  flame  of  hydrogen  issuing  from  a  fine 
jet,  as  in  Fig.  5  ;  the  glass  becomes  at  once  dimmed,  owing  to 


FIG,  5. 


the  condensation  of  water  in  small  drops  upon  the  cold  dry 
surface.  A  number  of  these  drops  can  be  collected,  and,  upon 
examination,  are  found  to  consist  of  pure  water.  Hydrogen 
does  not  support  the  combustion  of  a  candle,  nor  the  life  of 
an  animal.  If  a  burning  taper  is  pushed  up  into  a  cylinder 
of  this  gas,  held  with  its  mouth  downwards,  the  hydrogen 
burns  at  the  mouth  of  the  jar  while  the  taper  is  extinguished  ; 
it  can,  however,  be  relit  by  the  flame  at  the  mouth.  Hydro 
gen  can  be  poured  from  one  vessel  to  another  in  the  air ;  but 
as  it  is  lighter  than  air  it  must  be  poured  upwards.  The 
specific  gravity  of  hydrogen,  when  air  is  taken  as  the  unit,  is 
found  to  be  0-0693 ;  but  for  several  reasons  we  shall  find  it 


1 8  Elementary  Chemistry. 

more  convenient  to  take  hydrogen  itself  as  our  unit,  and  com 
pare  the  weight  of  the  same  volumes  of  other  gases  with 
hydrogen  instead  of  air.  One  litre  of  hydrogen  gas  at  o°  C. 
and  760  mm.  pressure  weighs  0-08936  gramme.  Free  hydro 
gen,  like  oxygen,  has  never  been  obtained  in  the  liquid  or 
solid  state. 

If  we  concentrate  by  boiling  the  liquid  remaining  in  the 
flask  after  the  evolution  of  the  hydrogen,  we  find  that  white 
crystals  separate  out  when  the  liquid  cools  ;  these  consist  of 
zinc  sulphate.  A  given  weight  of  zinc  (with  sulphuric  acid 
and  water)  can  always  be  made  to  produce  a  certain  weight 
of  hydrogen,  and  a  certain  weight  of  zinc  sulphate  will  always 
be  formed.  It  is  found  by  experiment  that  2  parts  by  weight 
of  hydrogen  can  be  obtained  by  dissolving  65-2  parts  of  zinc 
with  the  formation  of  161-2  parts  of  zinc  sulphate. 

The  pupil  must  carefully  work  out  the  examples  and  exer 
cises  given  for  each  Lesson  at  the  end  of  the  book,  and  thus 
test  the  accuracy  of  his  knowledge. 


LESSON  III. 

Physical  Properties  of  Gases,  &c. 

IT  becomes  now  of  importance  to  ascertain  not  merely  the 
weights  of  oxygen  and  hydrogen  capable  of  being  evolved  by 
using  given  weights  of  potassium  chlorate  or  zinc,  but  likewise 
the  volume  of  each  gas  thus  obtained.  Before  we  can  enter 
into  these  calculations  there  are  several  important  preliminary 
subjects,  with  the  principles  of  which  we  must  make  ourselves 
acquainted. 

The  first  of  these  is  the  metric,  or  French  decimal  system 
of  weights  and  measures  ;  the  second  is  the  mode  of  measur 
ing  temperature,  and  the  construction  and  use  of  thermome 
ters,  together  with  the  laws  regulating  the  expansion  of  gases 
by  heat ;  whilst  the  third  relates  to  the  measurement  of  at 
mospheric  pressure  by  means  of  the  barometer,  and  the  laws 


Elementary  Chemistry.  19 

regulating  the  changes  which  variations  of  pressure  produce 


in  the  volumes  of  gases. 


Metric  System  of  Weights  and  Measures. 

There  are  several  distinct  advantages  to  be  gained  by  the 
adoption  of  this  system,  the  chief  of  which  is  that  the  system 
is  throughout  a  decimal  one,  and  hence  all  calculations  for  re 
duction,  such  as  occur  in  our  old  measures  (from  pennyweights 
to  tons,  or  from  inches  to  miles,  for  instance),  are  avoided.  A 
second  important  consideration  which  renders  our  use  of  this 
system  advisable,  is  that  it  is  now  generally  adopted  by  men  of 
science  in  all  countries.  The  starting  point  of  this  system  is 
the  establishment  of  a  unit  of  length  called  a  metre,  equal  to 
rather  more  than  our  yard  (more  exactly,  39'37  English 
inches).  This  metre,  like  all  other  standards  of  length,  is  an 
arbitrary  length  :  a  standard  metre  was  prepared,  and  of  this 
copies  are  made  for  use.* 

The  metre  is  divided  into  tenths,  hundredths,  and  thou 
sandths  ;  these  parts  are  termed  respectively,  decimetres,  cen 
timetres,  and  millimetres.  The  multiples  of  the  metre,  tens, 
hundreds,  and  thousands,  are  called  decametres,  hectometres, 
and  kilometres.  The  measures  of  area,  or  square  measure, 
and  those  of  capacity,  or  cubic  measure,  are  easily  obtained  ; 
we  have  square  metres  and  square  deci-,  centi-,  and  milli-me- 
tres  ;  we  have  also  cubic  metres,  and  cubic  deci-,  centi-,  and 

*  When  the  metre  was  first  made,  it  was  intended  to  give  it  a  length  which  should 
have  some  reference  to  the  earth's  circumference,  and  a  standard  was  made  which 

had  the  length  of  the part  of  the  distance  from  the  equator  to  the  pole,  as 

10,000,000 

measured  by  the  French  geometricians.  Subsequent  investigations  have,  however, 
proved  that  the  measurement  of  the  earth's  circumference  then  made  is  not  quite 
correct,  and  hence  the  metre  turns  out  to  be  not  quite  (although  very  nearly)  the 

—  part  of  the  true  distance  of  the  pole  from  the  equator.     The  value  of  the 
10,000,000 

metric  system  does  not  at  all  depend  upon  this  relation  between  the  earth's  circum 
ference  and  the  metre.  The  metre  is  the  length  of  the  bar  of  metal  carefully  pre 
served  in  Paris,  from  which  copies  have  been  taken  for  use. 


2O  Elementary  Chemistry. 

milli-metres  ;  and  we  have  the  square  and  cubic  measures  de 
rived  from  the  multiples  of  the  metre  in  the  same  way. 

10  decimetres i  metre. 

100  centimetres 

1,000  millimetres 

loo  square  decimetres i  square  metre. 

lo.ooo      "      centimetres     .... 
1,000,000       "      millimetres     .... 

1,000  cubic  decimetres        .     .     .    .     i  cubic  metre. 
1,000,000      "     centimetres       ....  " 

1,000,000,000      "    millimetres        ....  " 

The  measure  on  the  margin  is  one  decimetre  in 
length  ;  it  contains  10  centimetres  and  100  millime 
tres.  For  the  sake  of  simplicity  the  word  litre  is 
used  to  signify  i  cubic  decimetre  (rather  less  than  an 
English  quart). 

The  French  philosophers  who  arranged  this  metric 
system  wished  to  have  a  simple  relation  between  the 
measure  of  volume  and  that  of  weight,  and  they  de 
termined  to  take  as  their  unit  of  weight  the  weight 
of  i  cubic  centimetre  of  pure  water  of  the  tempera 
ture  of  4°  Centigrade,  weighed  at  Paris.  This  weight 
is  termed  a  gramme.  It  is  divided  like  the  metre 
into  tenths,  hundredths,  and  thousandths,  called  re 
spectively  deci-,  centi-,  and  milli-gramme  ;  whilst  to 
the  tens,  hundreds,  and  thousands  of  grammes  the 
names  deca-,  hecta-,  and  kilo-gramme  are  given.  (A 
table  showing  the  relation  between  the  weights  and 
measures  of  the  metric  system  and  those  commonly 
in  use  in  this  country  is  given  in  the  Appendix.) 


Measurement  of  Temperature. — Thermometers. 

Measurements  of  changes  of  temperature  are  always  effect 
ed  by  ascertaining  the  expansion  or  contraction  which  bodies 
undergo  by  alteration  of  temperature.  For  this  purpose 
liquids  are  generally  used,  as  solids  expand  too  little  and 


Elementary  Chemistry.  21 

gases  too  much  to  be  convenient  indicators.  Mercury  and 
alcohol  are  the  liquids  commonly  employed,  especially  the 
former,  because  its  rate  of  expansion  is  nearly  uniform,  and 
because  the  range  of  temperature  which  can  be  measured  by 
a  mercurial  thermometer  is  large,  this  metal  boiling  at  a  very 
high  temperature,  and  freezing  at  a  comparatively  low  one. 
Alcohol  is  used  when  very  low  temperatures  have  to  be  mea 
sured,  as  this  liquid  has  never  yet  been  frozen.  Air  thermo 
meters  are  only  used  in  very  delicate  experiments  in  physics. 
In  order  to  prepare  a  mercurial  thermometer  a  straight  piece 
of  glass  tubing,  having  a  bore  as  uniform  as  possible  through 
out  its  whole  length,  is  taken,  and  a  bulb  blown  upon  the  end. 
This  bulb,  together  with  the  whole  of  the  tube,  is  then  filled 
with  mercury,  and  heated  up  to  the  highest  temperature  which 
the  instrument  is  required  to  measure  ;  the  open  end  of  the 
tube  is  then  completely  closed,  whilst  full  of  mercury,  by  melt 
ing  the  glass  before  the  blowpipe.  The  thermometer  thus 
prepared  requires  graduating,  in  order  that  its  indications 
may  be  compared  with  those  of  any  other.  This  graduation  is 
effected  :  I.  By  plunging  .the  bulb  and  stem  in  finely-pow 
dered  and  melting  ice,  and  marking  on  the  stem  the  point 
where  the  mercury  stands.  2.  By  immersing  the  bulb  and 
stem  in  the  steam  given  off  from  water  boiling  in  a  metallic 
vessel,  and  marking  off  the  point  where  the  mercury  then 
stands.  Care  must  be  taken  during  this  last  experiment  that 
the  height  of  the  barometer  be  observed  ;  the  reasons  for  this 
precaution  will  be  explained  further  on.  Having  obtained 
these  two  fixed  points,  it  is  easy  to  adapt  a  scale  to  the  ther 
mometer.  Three  scales,  each  of  which  is  capable  of  being 
expressed  in  terms  of  the  others,  are  at  present  in  use  :  i. 
The  Centigrade  scale.  2.  Fahrenheit's  scale.  3.  Reaumur's 
scale.  In  the  Centigrade  scale  (which  we  shall  adopt,  it  being 
the  one  almost  universally  employed  in  scientific  works,  and 
in  general  use  on  the  Continent)  the  space  between  these  two 
points — called  respectively  the  freezing  and  boiling  points — 
is  divided  into  ico  equal  parts,  each  of  which  is  called  a  de 
gree  :  the  Zero  of  the  scale  is  placed  at  the  freezing  point,  so 


22 


Elementary  Chemistry. 


that  the  boiling  point  is  100°.  These  divisions  are  continued 
above  and  below  the  boiling  and  freezing  points,  and  those 
below  this  latter  are  characterized  by  a  minus  sign,  thus,  — 1° 
— 2°,  etc.  Fahrenheit  divided  the  same  space  into  180  equal 
parts,  each  of  which  is  called  a  degree  Fahrenheit ;  he  did 
not,  however,  commence  his  scale  at  the  freezing  point,  as  he 
erroneously  thought  that  he  had  obtained  the  greatest  possi 
ble  degree  of  cold  by  making  a  mixture  of  snow  and  salt ;  the 
temperature  of  this  mixture  he  found  to  be  32  of  his  degrees 
below  freezing  point ;  he  therefore  called  the  freezing  point 
32°.  In  Fahrenheit's  scale,  minus  num 
bers  are  employed  to  denote  those  tem 
peratures  below  the  Zero  of  his  scale  ; 
this  scale  is  the  one  in  common  use  in 
England,  but  is  the  most  inconvenient 
one  which  we  could  adopt.  Reaumur's 
scale  (used  in  Russia  and  Sweden)  re 
sembles  the  Centigrade  scale,  except 
that  the  space  between  the  freezing  and 
boiling  points  is  divided  in  80  equal 
points  ;  so  that  water  boils  at  80°  Reau 
mur.  The  connection  between  these 
three  scales  is  seen  at  a  glance  by  refer 
ence  to  fig.  6.  The  relation  between  the 
degrees  of  Fahrenheit,  Centigrade,  and 
Reaumur,  is  expressed  by  the  numbers  9,  5,  4.  In  converting 
from  degrees  Fahrenheit  to  Centigrade  or  Reaumur,  we  must 
remember  first  to  subtract  32  and  then  reduce  ;  whilst,  when 
passing  from  degrees  Centigrade  and  Reaumur  to  Fahrenheit, 
we  must  add  32  after  the  multiplication  and  division  is  com 
pleted. 

If  very  exact  measurements  are  required,  several  precau 
tions  must  be  taken  in  the  graduation  and  use  of  thermometers  ; 
thus,  for  instance,  the  tube  must  be  calibrated— that  is,  the 
irregularities  in  the  bore  must  be  determined  and  allowed  for, 
whilst  any  slight  alteration  in  the  position  of  the  freezing 
point  must  from  time  to  time  be  ascertained.  Different  mer- 


FIG.  6. 


Elementary  Chemistry.  23 

curial  thermometers  often  show  slight  differences  in  the  indi 
cations,  owing  to  the  unequal  expansion  of  different  kinds  of 
glass,  hence  it  is  necessary  in  exact  experiments  to  have  re 
course  to  the  air  thermometer.  * 

Expansion  of  Gases  by  Heat. 

Solid  and  liquid  bodies  expand  much  less  for  equal  incre 
ments  of  heat  than  gases  ;  they  also  all  expand  differently, 
whilst  all  gases  expand  alike,  or  very  nearly  so.  The  expansion 
of  solids  and  liquids  is  a  subject  with  which,  in  elementary 
chemistry,  we  have  little  to  do,  whilst  a  knowledge  of  the  laws 
regulating  the  expansion  of  gases  is  of  more  immediate  im 
portance.  It  has  been  found  by  exact  and  laborious  experi 
ment  that  all  gases  expand  ^l*  part  of  their  volume  at  o°  C. 
for  every  increase  in  temperature  of  i°  Centigrade  : 

Thus  273  volumes  of  air  or  hydrogen  at  o° 
become  274  "  "  i° 

U  0~r  "  <<  ">° 

«  276  K  «  3° 

"  "  t° 


The  decimal  fraction  corresponding  to  jf  j  is  0-003665  ;  i 
volume  of  air  at  o°  C.  becomes  1-003665  volumes  when  heated 
to  i°  C.  This  fraction  is  called  the  co-efficient  of  the  expan 
sion  of  gases*  If  we  require  to  know  the  volume  which  1,000 
cubic  centimetres  of  hydrogen  measured  at  o°  C.  will  occupy 
when  the  temperature  is  raised  to  20°,  we  must  remember  that 
the  alteration  in  bulk  takes  place  in  the  ratio  of  the  numbers 
273  to  273  +  20.  Hence  we  multiply  1,000  by  293  and  divide 
by  273.  If  we  require  to  know  what  the  volume  1,000  cbc. 

*  Regnault  and  Magnus  have  shown  that  hydrogen  gas  expands  rather  less  than 
atmospheric  air,  whilst  carbonic  acid  gas  expands  rather  more  than  air.  The  coef 
ficients  of  expansion  from  o°  to  100°  obtained  by  these  two  renowned  experimental 
ists  are  as  follows  : 

Regnault,  Magnus, 

Hydrogen     ....     o'366i4  0*36556 

Carbonic  acid    .     .    .     0^37099 


24  Elementary  Chemistry. 

measured  at  20°  C.  will  occupy  when  the  temperature  sinks  to 
o°,  we  have  to  remember  that  the  diminution  in  volume  fol 
lows  the  same  law,  and  that,  therefore,  293  vols.  at  20°  will 
become  273  vols.  at  oc.  If  we  have  1,000  cbc.  of  gas  at  20°, 
and  desire  to  know  the  volume  which  it  will  occupy  at  50°,  we 
have  in  like  manner  to  remember  that  273  +  20,  or  293  vols. 
at  20°,  become  273  +  50,  or  323  vols.,  at  50°  ;  and  then  we  can 
easily  find  the  alteration  in  volume  which  the  i,ooocbc.  of  gas 
will  undergo  when  heated  from  20°  to  50°. 

Relation  of  Volume  of  Gases  to  Pressure. 

When  a  gas  is  subjected  to  an  increase  of  pressure,  the 
volume  of  the  gas  becomes  less  ;  and  when  the  pressure  is 
withdrawn,  the  gas  immediately  expands  again,  and  occupies 
exactly  the  same  volume  which  it  did  before  the  pressure  was 
increased.  Solid  and  liquid  bodies  cannot  be  compressed  in 
the  same  way.  Gases  are  hence  known  as  compressible 
fluids,  and  liquids  as  incompressible  fluids  :  liquids,  however, 
really  are  compressible,  but  only  to  a  very  slight  extent :  like 
gases,  they  recover  their  original  volume  on  removal  of  the 
pressure.  The  law  representing  the  relation  between  the 
volumes  of  a  gas  and  the  pressures  to  which  the  gas  is  sub 
jected,  is  a  very  simple  one  :  it  is  termed  Boyle's  or  Ma- 
riotte's  Law,  from  the  names  of  the  discoverers  :  it  states 
that  the  'volume  occupied  by  any  gas  is  inversely  proportional 
to  the  pressure  to  which  it  is  subjected.  Thus,  for  instance, 
the  volume  i  under  pressure  I  becomes  the  volume  2  under 
the  pressure  £,  the  volume  3  under  the  pressure  \,  the 
volume  \  under  the  pressure  2,  and  the  volume  i  under  the 
pressure  3,  and  so  on.*  For  a  description  of  the  experimen 
tal  proof  of  this  law,  a  work  on  Physics  must  be  consulted. 

The   instrument  which   serves   to   measure    the   pressure 

*  This  law,  like  many  other  physic?.!  laws,  is  only  an  approximation  to  the  truth 
as  ascertained  by  exact  experiment.  No  gases  obey  the  law  exactly  when  high 
pressures  are  used,  and  many  deviate  perceptibly  ;  still,  as  these  deviations  are  but 
very  slight,  we  may  assume,  for  the  purpose  of  our  calculations,  the  absolute  truth 
•>f  the  law  of  Boy'e.  ' 


Elementary  Chemistry. 


exerted  by  the  air  is  termed  a  barometer.  (Fig.  7.)  This  in 
its  simplest  form  consists  of  a  straight  glass  tube,  about 
800  mm.  (33  inches)  in  length,  closed  at  one  end,  and 
furnished  with  a  millimetre  scale.  This  tube  is 
rilled  with  dry  mercury,  and  the  open  end 
placed  downwards  in  a  basin  containing  the 
same  metal.  It  is  then  seen  that  the  mercury 
sinks  in  the  tube  to  a  point  about  760  mm.  from 
the  surface  of  the  metal  in  the  basin :  it  is  sus 
tained  in  this  position  by  the  pressure  of  the 
air.  When  this  pressure  becomes  greater  the 
height  of  the  sustained  column  becomes  greater ; 
when  it  diminishes,  the  level  of  the  mercury  in 
the  tube  falls.  All  gases  generated  at  the 
earth's  surface  are  subject  to  this  pressure, 
and  their  volumes  increase  or  diminish  ac 
cording  to  the  above  law,  when  the  superin 
cumbent  pressure  becomes  less  or  greater. 
In  estimating  the  volume  of  hydrogen  which  FIG.  7. 

can  be  collected  from  a  given  weight  of  zinc  and 
sulphuric  acid,  it  is  clear  that  we  require  to  know  not  only  the 
temperature  at  which  the  gas  is  collected,  but  also  the  atmosphe 
ric  pressure  under  which  it  is  measured  ;  and  in  order  to  be  able 
to  compare  the  bulks  of  two  gases,  we  must  always  compare 
them  under  like  conditions  of  temperature  and  pressure.  For 
this  purpose  we  agree  to  compare  all  the  volumes  of  gases  at  the 
standard  temperature  of  o°  C.  and  under  the  standard  pres 
sure  of  760  millimetres  of  mercury.  Suppose  now  that  we 
desire  to  know  what  weight  of  potassium  chlorate  we  need  to 
take  in  order  to  fill  with  oxygen  gas  a  gasholder  having  a 
capacity  of  10  litres,  the  temperature  of  the  room  being  15° 
C.  and  the  barometer  standing  at  752  mm.  We  know  that 
(i)  122-6  parts  by  weight  of  potassium  chlorate  yield  48  of 
oxygen  ;  (2)  that  a  litre  of  oxygen  at  o°  C.  and  760  mm. 
weighs  1-4298  grms.  We  must  now  ask  what  will  10  litres  of 
oxygen  weigh  if  measured  at  15°  C.  and  under  the  pressure 
of  752  mm.  ?  Now,  10  litres  at  o°  and  760  mm.  will  become 

2 


26  Elementary  Chemistry. 

iox76ox(273+i5)^ia66l  at   I5oand752  mm.  ;  therefore, 

752x273 
if  10  litres  at  o°  and  760  mm.  weigh  14*298  grms.  10  litres  at 

15°  and  752  mm.  will  weigh  Iz:r2_— 13-411  grms.     Next  we 

v  I. ODD  I 

require  to  know  how  many  grammes  of  chlorate  will  furnish 
this  weight  of  oxygen  ;  as  every  122-6  parts  of  chlorate  yield 

48    parts   of    oxygen    we    shall    need  I2_  J*L3-4*  r .=  34-254 

48 

grms.  of  chlorate.  In  the  same  way  we  can  calculate,  for 
instance,  the  weight  of  zinc  and  sulphuric  acid  needed  to  in 
flate  a  balloon  of  the  capacity  of  150  cubic  metres  with  hydro 
gen,  when  the  thermometer  stands  at  11°  C.  and  the  barome 
ter  at  763  mm.  The  student  will  do  well  to  work  out  numer 
ous  examples  of  this  kind,  in  order  to  familiarize  himself  with 
these  methods  of  calculation  (see  Exercises  at  the  end  of  the 
book). 

It  may  be  as  well  here  to  mention  a  simple  mode  of  calcu 
lating  the  absolute  weight  of  a  given  volume  of  any  gas  at  o° 
and  760  mm.  depending  upon  the  fact,  which  will  become  evi 
dent  as  we  proceed,  that  the  densities  of  all  the  elements 
known  in  tJie  gaseous  state  are  identical  with  their  combining 
weights.* 

Thus  the  density  and  combining  weight  of  oxygen  are  alike 
16  ;  or,  oxygen  is  16  times  heavier  than  hydrogen  :  the  densi 
ty  and  combining  weight  of  nitrogen  are  alike  14  ;  or,  nitro 
gen  is  14  times  heavier  than  hydrogen;  the  density  of  chlo 
rine  is  35-5,  that  of  sulphur  vapor  32,  and  so  on.  Remem 
bering  this  fact,  it  is  easy  to  calculate  the  absolute  weight  of  a 
given  volume — say  one  litre  of  these  different  gases — when 
we  know  that  one  litre  of  hydrogen  at  the  standard  pressure 
.and  temperature  weighs  0*08936  grammes.  Thus  I  litre  of 
oxygen,  under  the  same  circumstances,  weighs 

16x0.08936  =  i -430  grms. 

*  Two  notable  exceptions  to  this  law  occur  in  the  case  of  phosphorus  and  arsenic, 
whose  vapors  possess  a  density  twice  as  great  as  that  requited  to  be  in  accordance 
with  the  above  law,  which  holds  good  for  all  other  gaseous  elements. 


Elementary  Chemistry.  27 

i  litre  of  nitrogen  weighs      I4xo'o8936  =  1-251  grms. 

chlorine  „        35-5  x  0-08936  =  3-172      „ 

„          sulphur  vapor       „  32  x  0*08936  =  2  '860      „ 

In  the  case  of  almost  all  compound  gases,  the  density  is  one- 
combining  weight.* 


Thus  the  density  of  water-gas,  or  steam,  is  JL  or  9  ;  that 
is,  it  is  nine  times  heavier  than  hydrogen  ;  the  density  of 
hydrochloric  acid  is  -^—  -  or  18.25  ;  that  of  ammonia,  — 

or     8.5  ;    that    of    carbonic    acid,  ^-  or    22.       Hence    the 

weights  of  i  litre  of  these  compounds  (estimated  at  o°  C.  and 
760  mm.)  are  as  follows  :  — 

I  litre  of  steam  weighs  .  .  9  x  0.08936 

„       ammonia                        „  .  .  8.5x0-08936 

„       hydrochloric  acid          „  .  .  18-25x0-08936 

„       carbonic  acid                 „  .  .  22  x  0-08936 

Diffusion  of  Gases. 

Another  physical  property  of  gases  is  that  of  diffusion. 
Gases  which,  when  mixed  together,  do  not  combine  chemi 
cally,  have  the  power  of  becoming  intimately  mixed  together, 
even  when  different  in  specific  gravity,  and  when  the  heavier 
gas  is  placed  at  the  bottom,  and  both  remain  at  rest.  This 
important  property  is  called  the  diffusive  power  of  'gases.  The 
rate  at  which  gases  diffuse  varies  greatly.  Thus,  a  bottle 
filled  with  hydrogen  lost  94.5  per  cent  of  this  gas  when  left 
exposed  to  the  air  in  the  same  time  as  that  in  which  a  bottle 
of  carbonic  acid  lost  only  47  per  cent,  of  this  gas  in  the  same 
way.  Gaseous  diffusion  goes  on  through  the  minute  pores  of 
certain  solids,  such  as  stucco,  or  thin  plates  of  graphite  ;  the 
different  diffusive  rates  of  air  and  hydrogen  may  be  well  seen 
by  fixing  a  thin  piece  of  graphite  on  to  one  end  of  a  glass 

*  The  exceptioDS  to  this  law  are  mentioned  under  the  several  compounds. 


28  Elementary  Chemistry. 

tube  open  at  the  other  end,  and  filling  this  with  hydrogen  ;  on 
plunging  the  open  end  into  water  a  steady  rise  of  this  liquid 
in  the  tube  is  noticed,  and  after  some  time  the  whole  of  the 
hydrogen  is  found  to  have  disappeared,  and  the  tube  to  con 
tain  only  pure  air.  Experiments  made  upon  this  subject  have 
shown  that  the  velocity  of  diffusion  of  different  gases  is  in 
versely  proportional  to  the  square  roots  of  their  densities  ; 
thus  4  volumes  of  hydrogen  will  pass  through  the  diaphragm 
in  the  same  time  that  i  volume  of  oxygen  is  able  to  do  so, 
oxygen  being  sixteen  times  as  heavy  as  hydrogen.  This  pro 
perty  of  gases  has  an  important  bearing  upon  the  atmosphere 
of  towns  and  dwelling-rooms,  which  is  kept  pure  to  a  great 
extent  by  this  diffusive  power  of  gases. 


LESSON  IV. 

Chemical  Compounds  of  Oxygen  and  Hydrogen. 

WE  are  acquainted  with  two  compounds  of  oxygen  and 
hydrogen,  namely : — 

(i.)  Water  or  Hydric  Oxide.  Symbol  H2O.  Combining 
Proportion  18,  Density  9. 

(2.)  Peroxide  of  Hydrogen  or  Hydric  Peroxide.  Symbol 
HaOa.  Combining  Proportion  34. 

Water,  H2O.  When  hydrogen  burns  in  the  air  water  is 
formed  by  the  union  of  the  former  gas  with  oxygen.  The  dis 
covery  of  the  composition  of  water  was  made  in  1781  by  Mr. 
Cavendish,  who  showed  that  two  volumes  of  hydrogen  unite 
with  one  volume  of  oxygen  to  form  water.  In  order  to  prove 
this,  Cavendish  made  a  mixture  of  these  gases  in  this  propor 
tion  by  volume  in  a  jar,  and  then  allowed  them  to  pass  into  a 
strong  dry  vessel  (Fig.  8),  from  which  the  air  had  been  pumped 
out.  By  means  of  two  platinum  wires  melted  through  the 
glass  (at  B),  an  electric  spark  could  be  passed  through  the 
mixture  of  the  two  gases,  causing  their  combination  ;  dew  was 
then  seen  to  be  deposited  upon  the  sides  of  the  vessel,  and, 


Elementary  Chemistry.  29 

when  the  stopcock  was  opened  under  water,  this  liquid  rushed 
in,  filling  the  whole  space  formerly  occupied  by  the  mixed 
gases.  Cavendish  weighed  the  glass  before  and  after  the  ex- 


FIG.  8. 

periment,  and  knowing  the  weight  of  gases  taken,  he  found 
that  the  weight  of  the  water  produced  was  the  same  as  that 
of  the  gases  which  combined.  Since  the  above-mentioned 
year,  the  exact  composition  of  water  has  been  made  the  sub 
ject  of  careful  synthetical  experiment  by  many  chemists,  and 
the  result  has  been  to  confirm  by  much  more  delicate  methods 
this  original  conclusion.  The  most  accurate  of  these  methods 
of  ascertaining  the  composition  of  water  is  a  modification  only 
of  that  originally  used  by  Cavendish.  We  use  for  this  pur 
pose  a  long,  accurately  graduated,  strong  glass  tube  called  a 
Eudiometer  (A,  Fig.  9),  open  at  one  end  and  closed  at  the 
other,  whilst  through  the  glass  at  the  top  are  melted  two  pla 
tinum  wires.  This  tube  is  first  filled  with  mercury,  and  in 
verted  mouth  downwards  over  a  trough  filled  with  this  metal 
(Fig.  9).  Hydrogen  gas  is  now  allowed  to  enter  the  tube,  and 
the  volume  admitted  measured  (suppose  equal  to  100  vo 
lumes)  ;  oxygen  gas  is  next  admitted"  and  the  volume  of  the 
two  mixed  gases  measured  (suppose  that  75  volumes  of  oxy 
gen  are  added).  In  making  this  experiment,  care  must,  how 
ever,  be  taken  that  the  tube  is  not  more  than  half  full  of  the 


30  Elementary  Chemistry. 

gaseous  mixture,  as  great  heat  is  evolved  by  the  combustion, 
and  hence  a  sudden  expansion  of  volume  occurs,  for  which 
reason  it  is  necessary  to  press  down  the  open  end  of  the  tube 
upon  a  plate  of  caoutchouc  placed  under  the  mercury.  An 
electric  spark  is  now  passed  through  the  gas  along  the  plati 
num  wires,  when  a  flame  is  seen  to  pass  down  through  the 
gas,  showing  that  combination  has  occurred.  As  soon  as  the 
,heat  caused  by  the  combustion  has  disappeared,  the  water 
produced  will  be  deposited  as  dew  upon  the  inside  of  the 
tube,  and  will  then  only  take  up  about  2-,f0-0  part  of  the  bulk 
which  its  constituent  gases  occupied,  so  that  its  volume  may 


FIG.  9. 

be  neglected  ;  when  the  bottom  of  the  eudiometer  is  opened 
the  column  of  mercury  in  the  tube  rises,  and  we  shall  then 
find  that  only  25  volumes  of  gas  remain,  and  this  turns  out 
to  be  pure  oxygen.  Thus  we  see  that  100  volumes  of  hydrogen 
require  exactly  50  volumes  of  oxygen  for  their  complete  com- 


Elementary  Chemistry.  31 

bustion.  By  a  modification  of  this  experiment,  it  can  be 
shown  that  the  volume  of  the  gaseous  water  formed,  occupies 
exactly  100  volumes ;  or  2  volumes  of  hydrogen  unite  with  I 
of  oxygen  to  form  2  volumes  of  steam,  hence  the  density  of 

16  +  2 

steam,  or  weight  of  I  volume  is  =9.     The  most  strik- 

2 

ing  method  of  demonstrating  the  composition  of  water  analy- 
"  tically  is  by  splitting  it  up  into  its  constituent  gases  by  means  of 
a  current  of  voltaic  electricity.  For  this  purpose  we  fill  a  glass 
vessel  (Fig.  10)  with  water  acidulated  with  sulphuric  acid  to 
enable  it  to  conduct  the  electricity,  and  bring  two  test  tubes 
filled  with  water  and  inverted  into  this  vessel  over  two  small 
platinum  plates  attached  to  wires  of  the  same  metal  passing 
through  the  caoutchouc  stopper  at  the  bottom  of  the  glass ; 
on  connecting  these  with  the  terminals  of  a  battery  of  three 


FIG.  io. 


or  four  of  Grove's  elements,  an  evolution  of  gas  from  each 
plate  is  noticed,  that  disengaged  from  the  plate  in  connection 
with  the  platinum  end  of  the  battery  is  found  to  be  pure  oxy 
gen,  whilst  that  coming  off  from  the  other  plate,  connected 


32  Elementary  Chemistry. 

with  the  zinc  end  of  the  battery,  is  pure  hydrogen  gas.  If  the 
two  tubes  be  graduated  it  will  be  seen  that  the  volume  of  the 
hydrogen  is  a  very  little  more  than  double  that  of  the  oxygen, 
for  owing  to  the  oxygen  being  rather  more  soluble  in  water 
than  hydrogen,  we  do  not  thus  get  quite  the  exact  propor 
tions.  In  order  to  collect  the  detonating  mixed  gases  evolved 
by  this  electrolytic  decomposition  of  water, 
an  apparatus  represented  in  Fig.  n  may 
be  employed. 

Oxygen  being  16  times  as  heavy  as  hy 
drogen,  and  these  gases  combining  to  form 
water  in  the  proportions  by  volume  of  one 
volume  of  the  former  to  two  of  the  latter, 
we  now  know  that  the  proportions  by 
FlG  IX  weight  in  which  these  gases  exist  in  water 

must  be  as*i6  to  2.  Ij;  is  nevertheless  most 
important  that  this  calculation  be  verified  by  direct  experi 
ment.  For  this  purpose  use  is  made  of  the  fact  that  copper 
oxide  when  heated  alone,  does  not  part  with  any  of  its  oxygen, 
but  when  heated  in  the  presence  of  hydrogen  it  parts  with  as 
much  oxygen,  as  will,  by  combining  with  the  hydrogen,  form 


water,  being  itself  wholly  or  partly  reduced  to  metallic  copper. 
If,  therefore,  we  take  a  known  weight  of  copper  oxide,  heat  it, 


Elementary  Chemistry.  33 

and  pass  pure  hydrogen  over  it  until  it  has  parted  with  all  its 
oxygen,  and  if  we  collect  and  weigh  all  the  water  thus  formed, 
and  likewise  weigh  the  remaining  metallic  copper,  we  shall 
have  made  a  synthesis  by  weight  of  water.  For  the  loss  in 
weight  of  the  copper  oxide  is  the  weight  of  oxygen  which 
has  combined  with  hydrogen  to  form  water  ;  and  the  difference 
between  this  weight  and  that  of  the  water  formed,  is  the 
weight  of  the  hydrogen  thus  combined.  The  arrangement 
originally  used  for  this  determination  is  represented  in  Fig.  12. 
The  hydrogen  is  purified  from  any  trace  of  arsenic,  sulphur, 
and  moisture  which  it  may  contain  by  passing  through  the 
U  tubes,  containing  absorbent  substances,  and  placed  in  a 
freezing  mixture.  Some  only  of  these  (A)  are  represented  in 
the  figure.  The  tube  B,  containing  a  very  hygroscopic  sub 
stance,  is  weighed  both  before  and  after  the  experiment,  and 
if  no  increase  occurs,  the  dryness  of  the  gas  is  insured.  The 
gas  then  comes  in  a. perfectly  pure  state  into  contact  with  the 
heated  copper  oxide  contained  in  the  bulb  C.  This  first  bulb, 
which  is  accurately  weighed,  is  placed  in  connection  with  a 
second  bulb  D,  in  which  the  water  formed  by  the  reduction 
of  the  oxide  collects  ;  any  moisture  which  may  escape  con 
densation  in  this  bulb  is  retained  in  weighed  drying  tubes,  E 
and  F,  containing  fragments  of  pumice  moistened  with  sul 
phuric  acid.  Most  careful  experiments  made  according  to 
this  method,  carried  out  with  many  precautions,  which  cannot 
here  be  detailed,  have  shown  that  88*89  Pai"ts  of  oxygen  by 
weight  unite  with  irn  parts  of  hydrogen  to  form  100  parts 
of  water. 

Free  oxygen  and  hydrogen  combine  together,  when  a  light 
is  brought  in  contact  with  them,  with  so  much  force  that  a 
violent  and  dangerous  explosion  occurs  from  the  sudden  ex 
pansion  caused  by  the  great  heat  evolved  in  combination.  If 
we  fill  a  strong  soda-water  bottle  one-third  full  with  oxygen 
and  two-thirds  with  hydrogen,  and  then  bring  a  flame  to  the 
mouth,  the  gases  combine,  producing  a  sudden  detonation 
like  the  report  of  a  pistol.  Many  fatal  accidents  have  oc 
curred  to  persons  who  have  carelessly  experimented  with  large 

2* 


34  Elementary  Chemistry. 

volumes  of  this  explosive  mixture.  In  order  to  exhibit  the 
great  heat  evolved  by  the  combination  of  the  two  gases  the 
oxyhydrogen  blowpipe  is  employed  ;  in  this  arrangement  the 
gases  are  contained  separately  in  two  caoutchouc  bags,  being 
only  brought  together  at  the  point  at  which  the  combination 
is  desired,  so  that  all  danger  of  explosion  is  avoided.  The 
flame  thus  produced  is  very  slightly  luminous,  but  its  tem 
perature  is  so  high,  that  the  most  difficultly  fusible  metols, 
such  as  platinum,  may  be  easily  melted  in  it,  whilst  iron  wire 
held  in  the  flame  burns  with  beautiful  scintillations,  forming 
an  oxide  of  iron. 

Water  exists  in  nature  in  three  forms  :  in  the  solid  form  as 
ice,  in  the  liquid  state  as  water,  and  in  the  gaseous  form  as 
steam.  At  all  temperatures  between  o°  and  100°  C.  it  takes 
the  liquid  form,  and  above  100°  it  entirely  assumes  the  gase 
ous  form  (under  the  ordinary  atmospheric  pressure  of  760  mm.). 
The  melting  point  of  ice  is  always  found  to  be  a  constant 
temperature,  and  hence  it  is  taken  as  the  zero  of  the  Centi 
grade  scale  ;  water  may,  however,  under  certain  conditions, 
be  cooled  below  o°  C.  without  becoming  solid  ;  still  ice  can 
never  exist  at  a  temperature  above  o°  C.  In  passing  from  the 
solid  to  the  liquid  state  water  becomes  reduced  in  volume, 
and  on  freezing,  a  sudden  expansion  (from  I  volume  to  I  '099) 
takes  place.  That  this  expansion  exerts  an  almost  irresis 
tible  force  is  well  illustrated  by  the  splitting  of  rocks  during 
the  winter.'  Water  penetrates  into  the  cracks  and  crevices 
of  the  rocks,  and  on  freezing  widens  these  openings  ;  this 
process  being  repeated  over  and  over  again,  the  rock  is  ul 
timately  split  into  fragments.  Hollow  balls  of  thick  cast-iron 
can  thus  easily  be  split  in  two  by  filling  them  with  water  and 
closing  by  a  tightly  fitting  screw  and  then  exposing  them  to  a 
temperature  below  o°  C. 

In  the  passage  from  solid  ice  to  liquid  water,  we  not  only 
observe  this  alteration  in  bulk,  but  we  notice  that  a  very  re 
markable  absorption,  or  disappearance  of  heat,  occurs.  This 
is  rendered  plain  by  the  following  simple  experiment : — Let 
us  take  a  kilogramme  of  water  at  the  temperature  o°,  and 


Elementary  Chemistry.  35 

another  kilogramme  of  water  at  79°  ;  if  we  mix  these,  the 
temperature  of  the  mixture  will  be  the  mean,  or  39°'5  ;  if, 
however,  we  take  I  kilogramme  of  ice  at  o°  and  mix  it  with  a 
kilogramme  of  water  at  79°,  we  shall  find  that  the  whole  of 
the  ice  is  melted,  but  that  the  temperature  of  the  resulting  2 
kilogrammes  of  water  is  exactly  o°  ;  in  other  words,  the 
whole  of  the  heat  contained  in  the  hot  water  has  just  sufficed 
to  melt  the  ice,  but  has  not  raised  the  temperature  of  the 
water  thus  produced.  Hence  we  see  that  in  passing  from 
the  solid  to  the  liquid  state  a  given  weight  of  water  takes  up 
or  renders  latent  just  so  much  heat  as  would  suffice  to  raise 
the  temperature  of  the  same  weight  of  water  through  79°  C.  ; 
the  latent  heat  of  water  is  therefore  said  to  be  79  thermal 
units — a  thermal  unit  meaning  the  amount  of  heat  required 
to  raise  a  unit  of  water  through  I  °  C.  When  water 
freezes,  or  becomes  solid,  this  amount  of  heat  which  is  neces 
sary  to  keep  the  water  in  the  liquid  form,  and  is  therefore  well 
termed  the  heat  of  liquidity,  is  evolved,  or  rendered  sensible. 
A  similar  disappearance  of  heat  on  passing  from  the  solid  to 
the  liquid  state,  and  a  similar  evolution  of  heat  on  passing 
from  the  liquid  to  the  solid  form,  occurs  with  all  substances  ; 
the  amount  of  heat  thus  rendered  latent  or  evolved  varies, 
however,  with  the  substance.  A  simple  means  of  showing 
that  heat  is  evolved  on  solidification  consists  in  obtaining  a 
saturated  hot  solution  of  Glauber's  salt  (sodium  sulphate), 
and  allowing  it  to  cool.  Whilst  it  remains  undisturbed,  it 
retains  the  liquid  form,  but  if  agitated,  it  at  once  begins  to 
crystallize,  and  in  a  few  moments  becomes  a  solid  mass.  If 
now  a  delicate  thermometer  be  plunged  into  the  salt  while  so 
lidifying,  a  sudden  rise  of  temperature  will  be  noticed.  Simi 
larly  water  at  rest  may  be  cooled  down  below  o°  C.  without 
solidifying,  but  if  agitated,  it  at  once  solidifies,  and  the  tem 
perature  of  the  whole  mass  instantly  rises  to  o°  C. 

When  water  is  heated from  o°  to  4°,  it  is  found  to  contract, 
thus  forming  a  striking  exception  to  the  general  law,  that 
bodies  expand  when  heated  and  contract  on  cooling ;  on  cool 
ing  from  4°  to  o°  it  expands  again  :  above  4°,  however,  it 


36  Elementary  Chemistry. 

follows  this  ordinary  law,  expanding  when  heated,  and  con 
tracting  when  cooled.  This  peculiarity  in  the  expansion  and 
contraction  of  water  may  be  expressed  by  saying  that  the 
point  of  maximum  density  of  water  is  4°  C.  ;  that  is,  a  given 
bulk  of  water  will  at  this  temperature  weigh  more  than  at  any 
other.  Although  the  amount  of  contraction  on  heating  from 
o°  to  4°  is  but  small  (i  volume  of  water  at  4°  becoming 
i +O-QOO 1 2  at  o°),  it  yet  exerts  a  most  important  influence 
upon  the  economy  of  nature.  If  it  were  not  for  this  appa 
rently  unimportant  property,  our  climate  would  be  perfectly 
arctic,  and  Europe  would  in  all  probability  be  as  uninhabitable 
as  Melville  Island.  In  order  better  to  understand  what  the 
state  of  things  would  be  if  water  obeyed  the  ordinary  laws 
of  expansion  by  heat,  we  may  perform  the  following  experi 
ment.  Take  a  jar  containing  water  at  a  temperature  above 
4°,  place  a  thermometer  at  the  top  and  another  at  the  bottom 
of  the  liquid.  Now  bring  the  jar  into  a  place  where  the  tem 
perature  is  below  the  freezing  point,  and  observe  the  tem 
perature  at  the  top  and  bottom  of  the  liquid  as  it  cools.  It 
will  be  seen  that  at  first  the  upper  thermometer  always  indi 
cates  a  higher  temperature  than  the  lower  one  ;  after  a  short 
time  both  thermometers  mark  4°  ;  and  as  the  water  cools  still 
further,  it  will  be  seen  that  the  thermometer  at  the  top  always 
indicates  a  lower  temperature  than  that  shown  by  the  one  at 
the  bottom  ;  hence  we  conclude  that  water  above  or  below 
4°  is  lighter  than  water  at  4°.  This  cooling  goes  on  till  the 
temperature  of  the  top  layer  of  water  sinks  to  o°,  after  which 
a  crust  of  ice  is  formed  ;  but  if  the  mass  of  the  water  be 
sufficiently  large,  the  temperature  of  the  water  at  the  bottom 
is  never  reduced  below  4°.  In  nature  precisely  the  same 
phenomenon  occurs  in  the  freezing  of  lakes  and  rivers  ;*  the 
surface-water  is  gradually  cooled  by  cold  winds,  and  thus 
becoming  heavier,  sinks,  whilst  lighter  and  warmer  water 
rises  to  supply  its  place :  this  goes  on  till  the  temperature  of 
the  whole  mass  is  reduced  to  4°,  after  which  the  surface-water 

*  The  point  of  maximum  density  of  sea-water  is  considerably  lower  than  that  of 
fresh,  and  is  in  fact  below  o°  C. 


Elementary  Chemistry.  37 

never  sinks,  however  much  it  be  cooled,  as  it  is  always  lighter 
than  the  deeper  water  at  4°.  Hence  ice  is  formed  only  at  the 
top,  the  mass  of  water  retaining  the  temperature  of  4°.  Had 
water  become  heavier  as  it  is  cooled  down  to  the  freezing 
point,  a  continual  circulation  would  be  kept  up  until  the 
whole  mass  was  cooled  to  o°,  when  solidification  of  the  whole 
would  ensue.  Thus  our  lakes  and  rivers  would  be  converted 
into  solid  masses  of  ice,  which  the  summer's  warmth  would 
be  quite  insufficient  to  melt  thoroughly  ;  hence  the  climate 
of  our  now  temperate  zone  might  approach  in  severity  that 
of  the  arctic  regions.  Sea-water  does  not  freeze  en  masse, 
owing  to  the  great  depth  of  the  ocean,  which  prevents  the 
whole  from  ever  being  cooled  down  to  the  freezing  point ; 
similarly,  in  England,  very  deep  lakes  never  freeze,  as  the 
temperature  of  the  whole  mass  never  gets  reduced  to  4°  C. 

In  passing  from  the  liquid  to  the  gaseous  state,  water 
exhibits  several  interesting  and  important  phenomena.  In 
the  first  place,  when  we  heat  water  to  100°  C.  it  begins  to 
boil,  or  enters  into  ebullition;  that  is,  a  rapid  disengage 
ment  of  water-gas,  or  steam,  from  the  lower  or  most  heated 
surface  takes  place  :  this  is  well  seen  when  water  is  heated 
in  a  glass  globe  over  a  gas  flame.  In  this  passage  from 
the  liquid  to  the  gaseous  state,  a  large  quantity  of  heat 
becomes  latent,  the  temperature  of  the  steam  given  off  being 
the  same  as  that  of  the  boiling  water,  as,  like  all  other  bodies, 
water  requires  more  heat  for  its  existence  as  a  gas  than  as  a 
liquid.  The  amount  of  heat  latent  in  steam  is  roughly  ascer 
tained  by  the  following  experiment.  Into  i  kilog.  of  water  at 
o°,  steam  from  boiling  water,  having  the  temperature  of  100", 
is  passed  until  the  water  boils  :  it  is  then  found  that  the  whole 
weighs  1-187  kilogs.  or  0-187  kilogs.  of  water  in  the  form  of 
steam  at  100°,  have  raised  I  kilog.  of  water  from  o°  to  100°  ; 
or  i  kilog.  of  steam  at  100°  would  raise  5-36  kilogs.  of  ice-cold 
water  through  100°,  or  536  killogs.  through  i°.  Hence  the 
latent  heat  of  steam  is  said  to  be  536  thermal  units. 

Water,  and  even  ice,  constantly  give  off  steam  or  aqueous 
vapor  at  all  temperatures,  when  exposed  to  the  air ;  thus  we 


38  Elementary  Chemistry. 

know  that  if  a  glass  of  water  be  left  in  a  room  for  some  days, 
the  whole  of  the  water  will  gradually  evaporate.  This  power 
of  water  to  rise  in  vapor  at  all  temperatures  is  called  the 
elastic  force,  or  tension,  of  -aqueous  vapor ;  it  may  be 
measured,  when  a  small  quantity  of  water  is  placed  above  the 
mercury  in  a  barometer,  by  the  depression  which  the  tension 
of  the  vapor  thus  given  off  is  capable  of  exerting  upon  the 
mercurial  column  (as  in  Fig.  7).  If  we  gradually  heat  the 
drops  of  water  thus  placed  in  the  barometer,  we  shall  notice 
that  the  column  of  mercury  gradually  sinks,  and  when  the 
water  is  heated  to  the  boiling  point,  the  mercury  in  the  baro 
meter  tube  is  found  to  stand  at  the  same  level  as  that  in  the 
trough,  showing  that  the  elastic  force  of  the  vapor  at  that 
temperature  is  equal  to  the  atmospheric  pressure.  Hence 
•water  boils  when  the  tension  of  its  vapor  is  equal  to  the 
superincumbent  atmospheric  pressure.  ^OrTthe  tops  of  moun 
tains,  where  the  atmospheric  pressure  is  less  than  at  the  sea's 
level,  water  boils  at  a  temperature  below  100°  ;  thus  at  Quito, 
where  the  mean  height  of  the  barometer  is  527  mm.,  the  boil 
ing  point  of  water  is  99°'!  ;  that  is,  the  tension  of  aqueous 
vapor  at  9^°'!  is  equal  to  the  pressure  exerted  by  a  column 
of  mercury  527  mm.  high.  Founded  on  this  principle,  an 
instrument  has  been  constructed  for  determining  heights  by 
noticing  the  temperatures  at  which  water  boils.  A  simple 
experiment  to  illustrate  this  fact  consists  in  boiling  water  in  a 
globular  flask,  into  the  neck  of  which  a  stopcock  is  fitted  :  as 
soon  as  the  air  is  expelled,  the  stopcock  is  closed,  and  the 
flask  removed  from  the  source  of  heat  ;  the  boiling  then 
ceases  ;  but  on  immersing  the  flask  in  cold  water,  the  ebulli 
tion  recommences  briskly,  owing  to  the  reduction  of  the  pres 
sure  consequent  upon  the  condensation  of  the  steam  ;  the 
tension  of  the  vapor  at  the  temperature  of  the  water  in  the 
flask  being  greater  than  the  diminished  pressure.  All  other 
liquids  obey  a  similar  law  respecting  ebullition  ;  but  as  the 
tensions  of  their  vapors  are  very  different,  their  boiling 
points  vary  considerably. 

When  steam  is  heated  alone,  it  expands  according  to  the 


Elementary  Chemistry. 


39 


law  previously  given  for  permanent  gases,  but  when  water  is 
present,  and  the  experiment  is  performed  in  a  closed  vessel, 
the  elastic  force  of  the  steam  increases  in  a  far  more  rapid 
ratio  than  the  increase  of  temperature.  The  following  table 
gives  the  tension  of  aqueous  vapor,  as  determined  by  ex 
periment,  at  different  temperatures  measured  on  the  air 
thermometer. 

Tension  of  the  Vapor  of  Water. 


Temperature 
Centigrade. 

Tension  in 

millimetres  of 
mercury. 

Temperature 
Centigrade. 

Tension  in 
atmospheres, 
i  atmosphere 
=  760  mm.  of 
mercury. 

—20° 

0-927 

100° 

I 

IO 

2-093 

III-7 

i'S 

0 

4600 

I20'6 

2 

+  5 

6-534 

127-8 

2'5 

10 

9-l65 

133*9 

3 

15 

I2-699 

144-0 

4 

20 

I7-39I 

159-2 

6 

3° 

31'548 

170-8 

8 

40 

54-906 

180-3 

10 

5° 

91-982 

213-0 

20 

60 

148-791 

188-4 

12 

70 

233^93 

I95-5 

14 

80 

354-280 

201-9 

16 

90 

525-450 

2077 

18 

100 

760-000 

213-0 

20 

2247 

25 

We  now  see  why  the  barometric  height  must  be  noticed  in 
graduating  a  thermometer  (Page  21) ;  if  the  height  differ  from 
760  mm.  the  temperature  of  the  water  boiling  under  that  pres 
sure  will  not  be  quite  100°  C.  A  metal  vessel  is  here  em 
ployed,  because  it  is  found  that  water  does  not  always  boil  at 
1 00°  in  glass  vessels,  even  though  the  atmospheric  pressure 
be  760  mm.,  owing  to  some  molecular  action  analogous  to 
cohesion  between  the  glass  and  water. 


4o 


Elementary  Chemistry. 


Water  and  ice,  when  seen  in  large  masses,  are  found  to 
possess  a  blue  color ;  this  is  well  seen  in  the  glaciers  and 
lakes  of  Switzerland.  In  order  to  obtain  pure  water  the 
chemist  is  obliged  to  distil  river  or  spring-water  (that  is,  to 
boil  the  water  and  collect  the  water  formed  by  the  condensa 
tion  of  the  steam  thus  produced),  as  all  such  water  contains 
more  or  less  solid  matter  in  solution  derived  from  the  surface 
of  the  earth  over  which  the  water  flows  ;  this  dissolved  solid 
matter  is  left  behind  on  boiling  off  the  water.  Solid  matter  in 
suspension  can  be  got  rid  of  by  the  simple  process  &i filtration 
through  paper,  sand,  &c.  An  arrangement  for  distillation 
used  in  laboratories  is  seen  in  Fig.  13.  Rain-water  is  the 


FIG.  13. 

purest  form  of  water  occurring  in  nature,  but  even  this  con 
tains  impurities  derived  from  the  dust,  &c.  in  the  air,  and  no 
sooner  does  it  touch  the  earth's  surface  than  it  dissolves  some 
of  the  materials  with  which  it  comes  in  contact,  and  accord 
ing  to  the  nature  of  the  ground  over  which  it  passes  becomes 
more  or  less  impure.  All  fresh  water  on  the  earth's  surface 
has  been  derived  from  the  ocean  by  a  vast  process  of  distilla 
tion,  having  been  deposited  in  the  form  of  rain  or  snow  from 
the  atmosphere. 


Elementary  Chemistry.  41 

Water  is  the  most  general  solvent  for  chemical  substances 
with  which  we  are  acquainted.  Most  salts  are  soluble  to  a 
greater  or  less  extent  in  water,  and  are  deposited  again  in 
crystals  when  the  water  is  evaporated  ;  we  are  unacquainted 
with  any  simple  general  law  regulating  the  quantities  of  solids 
taken  up  by  water;  in  most  cases  the  solubility  is  greater  in 
hot  than  in  cold  water.  Water  is  also  contained  in  the  solid 
state  in  combination  as  water  of  crystallization  in  many  salts  ; 
when  this  water  is  driven  off  by  heat,  the  crystal  falls  to  pow 
der.  Gases  also  dissolve  in  water  in  quantities  varying  with 
the  nature  of  the  gas,  the  temperature,  and  the  pressure  to 
which  the  gas  is  subjected.  It  is  solely  in  consequence  of  the 
presence  of  oxygen  derived  from  the  air  dissolved  in  the  water 
of  lakes,  rivers,  and  seas,  that  fish  are  enabled  to  keep  up  their 
respiration  ;  as  the  water  passes  through  their  gills  the  oxygen 
is  taken  up  to  purify  their  blood. 

Hydric  Peroxide,  H2  O2.  This  is  a  substance  which  does 
not  occur  in  nature,  but  is  artificially  prepared  by  acting  on 
barium  peroxide  Ba  O2  with  hydrochloric  acid  H2  C12  ;  an  ex 
change  takes  place  between  the  barium  and  hydrogen,  giving 
rise  to  hydric  peroxide  and  barium  chloride.  Thus 

Ba    I     02 

C12    I    H2 

It  has  received  the  name  of  oxygenated  water,  as  it  easily  de 
composes  into  oxygen  and  water :  it  is  found  to  contain  twice 
as  much  oxygen  as  water  does,  consisting  of  2  parts  by  weight 
of  hydrogen  combined  with  32  of  oxygen  ;  hence,  if  we  repre 
sent  water  by  the  symbol  H2O,  hydric  peroxide  will  be  writ 
ten  H2  O2. 

Hydric  peroxide  acts  as  a  powerful  bleaching  agent,  owing 
to  the  ease  with  which  it  parts  with  half  its  oxygen,  thus  ox 
idizing  the  coloring  matters  ;  but  owing  to  the  difficulty  at 
tending  its  preparation,  it  has  not  been  applied  to  this  pur 
pose  on  a  large  scale. 

In  addition  to  water  and  hydric  peroxide,  we  are  acquainted 
with  no  compounds  of  oxygen  and  hydrogen. 


42  Elementary  Chemistry. 


LESSON  V. 

NITROGEN.     Symbol  N.     Combining  Proportion  14. 
Density  14. 

NITROGEN  exists  in  the  free  state  in  the  air,  of  which  it  con 
stitutes  four-fifths  by  bulk  ;  it  occurs  combined  in  the  bodies 
of  plants  and  animals  in  various  chemical  compounds,  such 
as  nitre,  whence  the  gas  derives  its  name  (generator  of  nitre). 
It  is  best  obtained  from  the  air  by  taking  away  the  oxygen 
with  which  it  is  mixed  ;  for  this  purpose  we  may  burn  a  piece 
of  phosphorus  in  a  bell-jar  filled  with  air,  the  mouth  of  which 
is  placed  in  a  vessel  full  of  water.  White  fumes  of  a  com 
pound  of  phosphorus  and  oxygen,  phosphoric  pentoxide,  at 
first  fill  the  jar,  but  these  soon  subside  and  dissolve  in  the 
water,  leaving  the  nitrogen  in  a  nearly  pure  state.  One-fifth 
of  the  original  volume  of  the  air,  consisting  of  oxygen,  will 
have  disappeared.  Nitrogen  may  also  be  prepared  by  pass 
ing  air  over  red-hot  metallic  copper,  which  combines  with  the 
oxygen,  forming  a  solid  compound,  and  leaving  the  gaseous 
nitrogen  in  a  pure  state.  Nitrogen  is  also  formed  when  a  cur 
rent  of  chlorine  is  passed  through  an  excess  of  a  solution  of 
ammonia ;  nitrogen  gas  is  evolved,  and  sal-ammoniac  remains 
behind  in  solution.  If  the  chlorine  be  present  in  excess,  a 
most  dangerous  and  explosive  compound  is  formed.  Nitro 
gen  is  a  colorless  and  tasteless  inodorous  gas  slightly  lighter 
than  air  (specific  gravity  0*972,  air  being  i.o).  It  does  not 
combine  readily  with  bodies,  and  is  a  very  inert  substance, 
neither  supporting  combustion  nor  animal  life,  nor  burning  it 
self:  it  has,  however,  no  poisonous  properties,  and  animals 
plunged  into  a  jar  of  this  gas  die  simply  of  suffocation  from 
the  want  of  oxygen.  Nitrogen  can  be  made  to  unite  with  both 
oxygen  and  hydrogen  ;  when  combined  with  the  latter  it  forms 
a  powerful  alkaline  base,  ammonia,  and  united  with  both  ele 
ments  it  forms  a  strong  acid,  nitric  acid. 


Elementary  Chemistry.  43 


The  Atmosphere. 

The  Atmosphere  is  the  gaseous  envelope  encircling  the 
earth  ;  and  it  constitutes  the  ocean  of  air  at  the  bottom  of 
which  we  live.  We  become  aware  of  the  existence  of  the  air 
when  we  move  rapidly,  and  experience  the  resistance  offered 
to  the  passage  of  our  bodies,  and  also  when  the  air  is  in  mo 
tion  giving  rise  to  a  wind.  We  notice  the  pressure  of  the  at 
mosphere  if  we  withdraw  the  air  from  beneath  the  hand  by  a 
powerful  airpump,  for  we  then  find  that  the  hand  is  pressed 
down  with  a  force  equal  to  i'O33  kilogs.  on  a  square  centi 
metre,  or  nearly  15  Ibs.  on  every  square  inch.  The  total  at 
mospheric  pressure  which  the  human  body  has  to  support 
hence  amounts  to  several  tons,  but  this  pressure  is  not  felt  un 
der  ordinary  circumstances,  because  the  pressure  is  exerted 
equally  in  every  direction.  The  instrument  used  for  measur 
ing  the  pressure  of  the  air  is  termed  a  Barometer  (see  Fig.  7, 
p.  25),  and  the  average  pressure  at  the  sea  level  is  equal  to 
that  exerted  by  a  column  of  mercury  760  mm.  high.  The  air 
being  elastic  and  having  weight,  it  is  clear  that  the  lower  lay 
ers  of  air  must  be  more  compressed  than  those  above  them, 
and  hence  the  density  of  the  air  must  vary  at  different  heights 
above  the  sea  level.  The  density  of  the  air  being  thus  de 
pendent  on  the  pressure  to  which  it  is  subjected,  the  higher 
strata  of  air  become  extremely  rarified,  and  it  is  hence  diffi 
cult  to  say  exactly  whereabouts  the  air  ceases,  but  it  appears 
that  the  limit  of  the  atmosphere  is  about  45  miles  from  the 
level  of  the  sea.  If  the  whole  atmosphere  were  of  the  same 
density  throughout  as  it  is  at  the  earth's  surface,  it  would  only 
reach  to  a  height  of  a  little  less  than  5  miles  above  the  sea 
level.  The  weight  of  one  litre  of  dry  air  at  o°  and  under  760 
mm.  of  pressure  is  F2932  grammes. 

Respecting  the  chemical  composition  of  the  atmosphere,  we 
have  to  remark,  in  the  first  place,  that  the  air  is  a  mixture,  and 
not  a  chemical  compound  of  its  constituent  gases,  although,  as 
we  shall  see,  these  occur  throughout  the  atmosphere  in  almost 
unvarying  proportions.  The  grounds  for  coming  to  this  con- 


44  Elementary  Chemistry. 

elusion  are.  first,  if  we  bring  oxygen  and  nitrogen  together  in 
the  proportions  in  which  they  are  found  in  air,  no  elevation  of 
temperature  or  alteration  in  bulk  occurs  (as  is  invariably  the 
case  when  gases  combine),  and  yet  the  mixture  acts  in  every 
way  like  air  ;  secondly,  that  the  relative  quantities  of  the  two 
gases  present  are,  not  those  of  their  combining  weights,  nor 
of  any  simple  multiples  of  these  weights,  and  that  although 
in  general  the  proportions  of  the  two  gases  are  constant,  yet 
instances  not  unfrequently  occur  in  which  this  ratio  is  differ 
ent  from  the  ordinary  one.  The  most  convincing  proof,  how 
ever,  that  air  is  not  a  chemical  compound,  is  derived  from  an 
experiment  upon  the  solubility  of  air  in  water  :  when  air  is 
shaken  up  with  a  small  quantity  of  water,  some  of  the  air  is 
dissolved  by  the  water  ;  this  dissolved  air  is  easily  expelled 
again  from  the  water  by  boiling,  and  on  analysis  this  expelled 
air  is  found  to  consist  of  oxygen  and  nitrogen  in  the  relative 
proportions  of  I  and  1*87.  Had  the  air  been  a  chemical 
compound,  it  would  be  impossible  to  decompose  it  by  simply 
shaking  it  up  with  water  ;  the  compound  would  then  have  dis 
solved  as  a  whole,  and  on  examination  of  the  air  expelled  by 
boiling,  it  would  have  been  found  to  consist  of  oxygen  and 
nitrogen  in  the  same  proportions  as  in  the  original  air,  viz.  as 
i  to  4.  This  experiment  shows,  therefore,  that  the  air  is  only 
a  mixture,  a  larger  proportion  of  oxygen  being  dissolved  than 
corresponds  to  that  contained  in  the  atmosphere,  owing  to 
this  gas  being  more  soluble  in  water  than  nitrogen. 

There  are  many  ways  of  determining  the  amounts  of  oxy 
gen  and  nitrogen  contained  in  the  air,  the  best  of  these  being 
by  the  eudiometer  j*  by  means  of  which  the  composition  by 
volume  is  ascertained.  For  this  purpose  the  same  arrange 
ment  is  employed  as  that  used  in  the  eudiometric  synthesis 
of  water.  (Fig.  14.)  A  quantity  of  air  sufficient  to  fill  the 
tube  about  one-sixth  full  is  introduced  into  the  eudiometer 
previously  filled  with  mercury  ;  the  volume  of  this  air  is  then 
accurately  ascertained  by  reading  off  with  a  telescope  the 


*  From  evfiios,  good,  and  pirpvv,  a  measure  :  a  measure  of  the  goodness  or 
healthiness  of  the  air,  that  is,  of  the  quantity  of  oxygen  which  it  contains. 


Elementary  Chemistry. 


45 


number  of  the  millimetre  divisions  on  the  tube  to  which  the 
mercury  reaches,  whilst  the  height  of  the  column  of  mercury 
in  the  tube  above  the  trough,  together  with  that  of  the  ba 
rometer,  and  the  temperature  of  the  air,  are  also  read  off. 
Such  a  quantity  of  pure  hydrogen  gas  is  now  added  as  is  more 
than  sufficient  to  combine  with  all  the  oxygen  present ;  and 
the  volume  of  this  gas,  and  the  pressure  exerted  upon  it,  are 
then  determined  as  before.  An  electric  spark  is  now  passed 
through  the  mixture,  care  having  been  taken  to  prevent  any 
escape  of  gas  by  pressing  the  open  end  of  the  eudiometer 
against  a  sheet  of  caoutchouc  under  the  mercury  in  the 


FIG.  14. 

trough.  After  the  explosion  the  volume  is  again  determined 
as  before,  and  is  found  to  be  less  than  that  before  the  explo 
sion,  the  whole  of  the  oxygen  and  part  of  the  hydrogen  having 
combined  to  form  water  ;  the  diminution,  therefore,  repre 
sents  exactly  the  volumes  of  these  gases  which  have  united. 
We  know,  however,  from  our  previous  experiments  upon  the 
composition  of  water,  that  2  vols.  of  hydrogen  always  unite 
with  i  vol.  of  oxygen  to  form  water  ;  hence  one-third  of 


46  Elementary  Chemistry. 

the  diminution  in  volume  must  represent  the  oxygen  which 
has  disappeared,  and,  therefore,  the  volume  of  oxygen  con 
tained  in  the  air  taken.  An  example  may  make  this  clearer. 
Suppose  the  volume  of  air  taken  amounted  to  100  vols.  and 
that  after  the  addition  of  hydrogen  the  volume  of  the  mixture 
was  150  vols.  ;  after  the  explosion  87  vols.  were  found  to 

remain,    that    is,    63    vols.    had    disappeared  ;    then  _A— 21 

will  be  the  volume  of  oxygen  contained  in  100  vols.  of  air. 

Analyses  of  air  collected  in  various  parts  of  the  globe  thus 
made  with  the  greatest  care  have  shown  that  the  relative 
quantities  of  oxygen  and  nitrogen  remain  the  same,  or  very 
nearly  the  same,  from  whatever  region  the  air  may  have  been 
taken.  So  that  whether  the  air  be  derived  from  the  tropics, 
or  the  arctic  seas,  from  the  bottom  of  the  deepest  mine  or  from 
an  elevation  of  20,000  feet  above  the  earth's  surface,  it  con 
tains  from  2O'9  to  21  vols.  of  oxygen  per  cent. 

When  we  know  the  composition  of  air  by  volume  and  the 
relative  densities  of  the  two  constituent  gases  (14  for  nitrogen 
and  1 6  for  oxygen),  we  can  calculate  its  composition  by 
weight  ;  we  thus  find  that  in  100  grms.  of  air  23' 1 6  grms.  of 
oxygen  are  mixed  with  76'84  grms.  of  nitrogen.  It  is  im 
portant  to  control  this  calculation  by  experiment ;  for  this 
purpose  a  large  glass  globe  furnished  with  a  stopcock  is  ren 
dered  vacuous  by  the  airpump  and  then  weighed  ;  a  tube  of 
hard  glass  filled  with  copper  turnings  and  also  furnished  with 
stopcocks  is  likewise  weighed.  This  tube  is  then  heated  to 
redness  in  a  long  tube-furnace,  and  connected  at  one  end 
with  the  empty  flask,  at  the  other  with  a  series  of  tubes  filled 
with  caustic  potash  and  sulphuric  acid,  for  the  purpose  of 
completely  freeing  the  air  passing  through  them  from  carbonic 
acid  and  aqueous  vapor  ;  the  cocks  are  then  slightly  opened 
and  air  allowed  to  pass  slowly  through  the  purifiers  into  the 
hot  tube,  where  it  is  completely  deprived  of  oxygen  by  the  hot 
metallic  copper  which  is  thereby  oxidized  ;  the  nitrogen 
passes  on  alone  into  the  empty  flask.  After  the  experi 
ment  is  concluded,  the  cooled  tube  is  again  weighed,  and  the 


Elementary  Chemistry. 


47 


increase  over  the  former  weighing  gives  the  quantity  of  oxy 
gen,  whilst  the  increase  in  weight  of  the  globe  gives  the 
nitrogen.  The  mean  of  a  large  number  of  experiments  thus 
made  shows  that  100  parts  by  weight  of  air  contained  23  parts 
by  weight  of  oxygen  and  77  of  nitrogen. 

In  addition  to  the  two  above-mentioned  gases,  the  air  con 
tains  several  other  important  constituents,  especially  carbonic 
.acid  gas,  aqueous  vapor,  and  ammonia  gas.  We  have 
already  noticed  (page  n)  the  important  part  which  the  car 
bonic  acid  gas  of  the  air  plays  in  the  phenomena  of  vegetation, 
this  gas  being  the  source  from  which  plants  obtain  the  car 
bon  they  need  to  form  their  tissues.  The  quantity  of  carbonic 
acid  present  in  the  air  is  very  small  compared  with  the  quan 
tities  of  oxygen  and  nitrogen,  being  only  about  4  vols.  to 
10,000  of  air  ;  nevertheless  the  absolute  quantity  of  this  gas 
contained  in  the  whole  atmosphere  is  enormously  large  (viz. 
about  3,000  billion  kilogs.)  The  quantity  of  carbonic  acid 
contained  in  the  air  can  be  found  by  drawing  a  known  volume 
of  perfectly  dry  air  (not  less  than  20  litres)  through  weighed 
tubes  containing  caustic  potash  ;  the  increase  in  weight  of 
the  tubes  gives  the  weight  of  carbonic  acid  contained  in  the 
air  drawn  through.  Fig.  15  shows  the  arrangement  of  the 


•Sfl 


FIG.  15. 


apparatus  ;  on  the  left  is  the  aspirator,  which  by  means  of  the 
flow  of  a  known  volume  of  water  from  the  top  to  the  bottom 


48  Elementary  Chemistry. 

vessel  causes  the  passage  of  an  equal  volume  of  air  through 
the  tubes  ;  the  two  tubes  farthest  from  the  aspirator  contain 
pumice-stone  steeped  in  sulphuric  acid,  and  serve  to  dry  the 
air  completely  before  passing  into  the  next  tube  and  potash 
bulbs,  in  which  the  carbonic  acid  is  absorbed  by  caustic 
potash  :  the  tube  nearest  the  aspirator  also  contains  sulphuric 
acid  and  pumice  to  avoid  a  loss  of  moisture  from  the  potash 
solution  in  the  bulbs.  The  quantity  of  carbonic  acid  con 
tained  in  the  air  in  different  localities  and  under  different  cir 
cumstances  varies  considerably — from  2  to  more  than  10  in 
10,000  vols.  of  air.  In  houses  and  closed  inhabited  spaces, 
the  quantity  of  carbonic  acid  present  is  often  much  larger, 
and  the  object  of  ventilation  is  to  reduce  the  quantity  of  car 
bonic  acid  to  as  low  a  point  as  possible.  Other  methods  for  the 
estimation  of  carbonic  acid  are  described  in  the  larger  manuals. 
Aqueous  vapor  is  contained  in  the  air  in  quantities  vary 
ing  in  different  localities  and  at  different  times,  and  depend 
ing  mainly  upon  the  temperature  of  the  air.  Air  at  a  given 
temperature  cannot  contain  more  than  a  certain  quantity  of 
moisture  in  solution,  and  when  it  has  taken  up  this  maximum 
quantity,  it  is  said  to  be  saturated  with  aqueous  vapor.  The 
higher  the  temperature  of  the  air,  the  more  water  can  it  retain 
as  vapor,  and  when  air  saturated  with  moisture  is  cooled, 
the  water  is  deposited  in  the  liquid  form  in  very  small  glo 
bules,  forming  a  mist,  fog,  or  cloud.  This  is  the  cause  of  the 
fall  of  rain,  snow,  and  hail  ;  when  warm  air  heavily  laden  with 
moisture  from  the  ocean  passes  into  a  higher  and  colder  posi 
tion,  or  meets  with  a  current  of  air  of  lower  temperature,  it 
cannot  any  longer  retain  so  much  aqueous  vapor,  and  a 
large  quantity  assumes  the  liquid  form,  falling  as  rain  when 
the  temperature  is  above  the  freezing  point,  or  crystallizing  as 
snow-flakes  if  the  temperature  be  below  that  point.  Hail  is 
caused  by  the  congelation  of  raindrops  by  passing  through  a 
stratum  of  air  below  the  freezing  point.  The  quantity  of  rain 
thus  deposited  is  very  large  :  i  cubic  metre  of  air  saturated 
with  moisture  at  25°  C.  contains  22-5  grms.  of  water,  and  if 
the  temperature  of  this  air  be  reduced  to  o°  C.,  it  will  then  be 


Elementary  Chemistry.  49 

capable  of  retaining  only  5^4  grms.  of  water  vapor  ;  hence 
1 7* i  grms.  of  water  will  be  deposited  as  rain.  The  air  in 
England  is  often  saturated  with  moisture,  whilst  the  driest  air 
observed  on  the  coast  of  the  Red  Sea  during  a  simoom  con 
tained  only  one-fifteenth  of  the  saturating  quantity.  Instru 
ments  for  ascertaining  the  degree  of  moisture  or  humidity  of 
the  air  are  termed  hygrometers. 

„  The  deposition  of  dew  is  caused  by  the  rapid  cooling  of  the 
earth's  surface  by  radiation  after  sunset,  and  by  the  conse 
quent  cooling  of  the  air  near  the  ground  below  the  tempera 
ture  at  which  it  begins  to  deposit  moisture. 

The  amount  of  aqueous  vapor  contained  in  the  air  at  any 
time  can  be  determined  by  the  apparatus  used  for  the  estima 
tion  of  the  carbonic  acid,  for  the  moisture  must  be  removed 
from  the  air  before  the  carbonic  acid  can  be  absorbed,  and 
the  increase  in  weight  of  the  tubes  filled  with  pumice-stone 
moistened  with  sulphuric  acid  gives  the  weight  of  aqueous 
vapor.  In  general  the  air  contains  from  50  to  70  per  cent, 
of  the  quantity  necessary  to  saturate  it.  If  the  quantity  be 
not  within  these  limits  the  air  is  either  unpleasantly  dry  or 
moist. 

The  next  important  constituent  of  the  air  is  ammonia, 
which  is  a  compound  of  nitrogen  and  hydrogen,  and  only 
exists  in  comparatively  very  minute  quantities  (about  I  part 
in  1,000.000  of  air).  Nevertheless  it  plays  a  very  important 
part,  as  it  is  mainly  from  this  ammonia  that  vegetables  obtain 
the  nitrogen  which  they  need  to  form  their  seeds  and  fruit  ; 
for  it  appears  that  plants  have  not  the  power  of  assimilating 
the  free  nitrogen  of  the  atmosphere.  '  Other  substances  which 
occur  in  the  atmosphere  in  very  small  quantities  may  be  con 
sidered  as  accidental  impurities.  Amongst  them,  volatile 
organic  matter  is  the  most  important,  as  probably  influencing 
to  a  great  extent  the  healthiness  of  the  special  situation.  We 
become  aware  of  the  existence  of  such  organic  putrescent 
substances  when  entering  a  crowded  room  from  the  fresh  air  ; 
and  it  is  probable  that  the  well-known  unhealthiness  of 
marshy  and  other  districts  is  owing  to  the  presence  of  some 


50  Elementary  Chemistry. 

organic  impurity.  At  present,  however,  we  possess  but  little 
certain  knowledge  on  this  subject.  Ozone  is  also  present  in 
fresh  air,  but  generally  absent  in  the  close  air  of  towns  and 
dwelling- rooms,  owing  to  its  decomposition  by  the  organic 
matter,  &c.,  in  such  air  ;  we  do  not  know  how  it  is  formed  in 
nature,  unless  it  be  by  the  discharge  of  atmospheric  elec 
tricity. 


LESSON  VI. 


Compounds  of  Nitrogen  with  Oxygen. 

WE  are  acquainted  with  five  distinct  chemical  compounds  of 
nitrogen  with  oxygen,  viz.  : 

1  Nitrous  Oxide,  containing  28  parts  by  weight  of  N  to  16  of  Q 

2  Nitric  Oxide,  "          28  "  "  32  —        h  °Q^ 

3  Nitric   Tri-oxide,    "          28  "  "  48  — 

4  Nitric  Tetr-oxide,  "          28  "  "  64  — 

5  Nitric  Pent-oxide,  "          28  "  "  So  — 

It  will  be  seen  that  the  oxygen  contained  in  these  com 
pounds  is  in  the  proportion  of  the  numbers  i,  2,  3,  4,  5,  to 
one  and  the  same  quantity  of  nitrogen  ;  and  here,  for  the  first 
time,  we  meet  with  a  striking  example  of  the  law  of  chemical 
combination  in  multiple  proportion.  Thus,  while  28  parts  by 
weight  of  nitrogen  combined  with  16  parts  of  oxygen  form 
44  parts  of  nitrous  oxide,  we  find  that  any  other  compounds 
of  these  two  elements  contain  some  simple  multiple  of  16 
parts  by  weight  of  oxygen  (thus,  either  2  x  16.  3  x  16,  4X  16, 
or  5  x  1 6),  and  that  no  compounds  exist  containing  any  inter 
mediate  quantity  of  oxygen. 

This  law  of  multiple  proportions  was  first  enunciated  by 
Dalton,  and  is  the  expression  of  well-established  experi 
mental  facts.  Dalton  endeavored  to  explain  these  facts  by 


Elementary  Chemistry.  51 

his  celebrated  Atomic  Theory.  He  asked  himself,  Why  do 
the  elements  combine  only  in  multiples  of  their  several  com 
bining  proportions  ?  and  he  answered  the  question  by  the 
following  supposition. 

Matter  is  made  up  of  small  indivisible  portions,  which  he 
called  Atoms  (d,  privative,  and  ta'^w,  I  cut).  These  atoms  do 
not  all  possess  the  same  weights,  but  the  relation  between 
..their  weights  is  represented  by  that  of  the  combining  weights 
of  the  elements  ;  thus  he  supposed  the  atom  of  oxygen  to  be 
1  6  times  as  heavy  as  the  atom  of  hydrogen,  and  the  weights 
of  the  atoms  of  nitrogen  and  oxygen  as  14  to  16.  Dalton 
further  assumed  that  chemical  combination  consists  in  the 
approximation  of  the  individual  atoms  to  one  another  ;  and, 
having  made  these  assumptions,  he  was  able  to  explain  why 
compounds  must  contain  their  constituents  in  the  combining 
proportions,  or  in  multiples  of  them,  and  in  no  intermediate 
proportion.  Let  us  take,  for  example,  the  compounds  of  ni 
trogen  and  oxygen  :  the  lowest  of  these  consists  of  one  single 
atom  of  oxygen  combined  with  2  atoms  of  nitrogen,  or  with 
one  double  atom  of  nitrogen,  as  it  contains  16  parts  of  oxygen 

to    28    of    nitrogen;    thus,  (j^)(^)(^)  >    anc*   we  therefore 

write  its  formula,  N2O,  and  call  it  nitrous  oxide.  The  next 
compound  that  can  be  formed  must  be  produced  by  the 
addition  of  another  atom  of  oxygen  to  this  ;  thus  we  get 

(fjVl^rojfoWNaOa,  or  nitric  oxide.  The  next  must  be 
formed  by  the  attachment  of  another  atom  of  oxygen,  and 
thus  we  get((o=N2O3,  or  nitric  tri-oxide. 


The  next  possible  compound  is 
or  nitric  tetr-oxide  ;*  and  the  next 


*  If  nitric  oxide  and  nitric  tetr-oxide  be  considered  to  be  represented  respec 
tively  by  the  formula  N.>  Oa  and  Na  O4.  they  will  be  exceptions  to  the  law  mentioned 
on  page  27,  respecting  the  density  of  compound  gases  or  vapors,  as  instead  of 
having  their  densities  represented  by  the  halves  of  their  combining  proportions, 
they  will  have  them  represented  by  the  quarters  of  these  numbers. 


52  Elementary  Chemistry. 

=  N2O6,  or  nitric  pent-oxide.  We  thus  see  that  an  atom 
being  indivisible,  no  intermediate  compounds  can  be  formed. 
In  considering  this  subject,  we  shall  do  well  to  remember 
that  the  law  of  multiple  proportions  being  founded  on  experi 
mental  facts,  stands  as  a  fixed  bulwark  of  the  science,  which 
must  ever  remain  true  ;  whereas  the  Atomic  Theory,  by  which 
we  now  explain  this  great  law,  may  possibly  in  time  give 
place  to  one  more  perfectly  suited  to  the  explanation  of  new 
facts. 

Nitrogen  and  oxygen  do  not  readily  combine  together,  but 
under  certain  circumstances  they  are  found  to  do  so  ;  thus, 
if  a  series  of  electric  sparks  are  passed  through  a  glass  vessel 
filled  with  dry  air,  the  presence  of  red  colored  vapors,  pos 
sessing  a  peculiar  acrid  smell,  is  soon  noticed.  These  con 
sist  of  nitric  tri-,  and  tetr-oxides,  formed  by  the  union  of  the 
nitrogen  and  oxygen  of  the  air.  If  an  alkali,  such  as  potash, 
be  present  in  the  air  through  which  the  sparks  are  passed,  a 
new  substance,  called  nitre,  or  potassium  nitrate,  is  formed ; 
and  from  this  an  important  compound,  called  nitric  acid,  can 
be  prepared.  This  substance  is  formed  when  flashes  of 
lightning  pass  through  the  air,  being  carried  down  to  the 
earth's  surface  in  the  rain.  Nitric  acid  may  be  considered 
as  a  compound  of  nitric  pentoxide  with  water  ;  and  as  all  the 
other  nitrogen  oxides  can  be  prepared  from  it,  we  shall  first 
consider  its  properties  and  mode  of  preparation. 

Nitric  Acid,  or  Hydric  Nitrate.— Symbol  H.NO3,  Com 
bining  Weight  63.  Nitre,  or  potassium  nitrate,  is  generally 
formed  by  the  gradual  oxidation  of  nitrogenous  animal  mat 
ter  in  presence  of  the  alkali  potash.  Spring  water,  especially 
the  surface  well-water  of  towns,  frequently  contains  nitrates 
in  solution,  owing  to  water  passing  through  soil  containing 
decomposing  animal  matters,  which  by  oxidation  yield  ni 
trates.  For  this  reason,  water  containing  nitrates  is  unfit  for 
drinking  purposes.  Potassium  Nitrate,  K  NO3  (commonly 
called  saltpetre)  occurs  as  an  incrustation  on  the  soil  in  various 
localities,  especially  in  India  ;  and  Sodium  Nitrate,  NaNOs, 
or  Chili  saltpetre,  is  found  in  large  beds  on  the  coast  of  Chili 


Elementary  Chemistry.  53 

and  Peru.     Nitric  acid,  H   NOs,  is  the  hydrogen  salt,   and 
hence    is    termed  Hydric  nitrate  :  it    may   be   regarded   as 

TJ    ~\ 

water,  ^  j-  O,  in  which  one  atom  of  hydrogen  is  replaced  by 
the  group  NO«,  thus,  ^Q    >  O  ;  it  is  obtained  by  heating  nitre, 


sulphuric  acid,  or  Dihydric  sulphate,  H2  SO4  ; 
when  nitric  acid,  H  NO3,  and  hydric  potassium  sulphate, 
HK  SO4,  are  formed.  The  decompositions  here  effected  may 
serve  as  the  type  of  a  very  large  number  of  chemical  changes 
classed  as  double  decompositions.  These  may  all  be  repre 
sented  as  consisting  in  an  exchange  between  two  elements, 
or  groups  of  elements  ;  thus  in  the  case  in  question,  one 
atom  of  the  hydrogen  in  the  sulphuric  acid  changes  place 
with  one  atom  or  its  equivalent  of  potassium  in  the  nitre. 
These  double  decompositions  .maybe  represented  in  the  form 
of  an  equation,  in  which  one  side  signifies  the  arrangement 
and  relative  weights  of  the  elements  before  combination, 
theother  the  arrangement  and  relative  weights  <K  the 
same  elements  after  the  chemical  change  has  taken  place, 
thus  — 


KNO3   +   H2S04     =     H  N03  +   HK  SO4* 

or,   Nitre  and  Sulphuric  Acid  give  Nitric  Acid  and  Hydric  Potassium  Sulphate. 

The  relative  weights  of  the  elements  and  compounds  entering 
into  the  decomposition  is  easily  ascertained  when  we  remem 
ber  that  each  symbol  expresses  not  merely  the  nature  of  the 
element,  but  also  the  relative  weight  with  which  it  combines, 
and  that  the  combining  weight  of  a  compound  is  the  sum  of 
the  combining  weights  of  its  constituents.  The  numbers  ex 
pressed  by  the  above  equation  are 

K          N        O3  +    H2    S        O4  =  H      N        O3    +   H  K        S  O4 

39'i    +    14   +   48   +    z    +    32    +   64  =  i    +    14    +    48    +     i   4-    39'!  +  32+64 

IQI'I  +  98  =63  +  136.1 

*  The  sign  +  placed  between  two  symbols  signifies  "  and  "  or  "  together  with." 


54 


Elementary  Chemistry. 


We  may  express  these  double  decompositions  perhaps 
more  clearly  by  representing  by  a  curved  line  the  actual 
exchange  of  hydrogen  for  potassium,  thus — 


or  by  a  straight  line,  thus — 

H  I  H  SO4 
NO3  |     K 

This  signifies  that  if  we  require  63  parts  by  weight  of  nitric 
acid  we  shall  require  to  take  exactly  ion  parts  of  nitre  and 
98  parts  of  sulphuric  acid,  and  that  we  shall  have  136-1  parts  of 
hydric  potassium  sulphate  formed.  Knowing  these  numbers, 


FIG.  16. 


it  is  easy  to  calculate  the  proportions  of  ingredients  needed 
to  produce  any  given  quantity  of  nitric  acid. 

Nitric  acid  is  prepared  on  a  small  scale  by  placing  equal 
weights  of  nitre  and  sulphuric  acid  in  a  stoppered  retort,  which 
is  gradually  heated  by  a  Bunsen's  burner,  as  in  Fig.  16 : 


Elementary  Chemistry.  55 

the  nitric  acid  formed  distils  over,  and  may  be  collected  in  a 
flask  cooled  with  water.  On  a  large  scale  this  substance  is 
prepared  in  iron  cylinders,  into  which  the  charges  of  nitre 
and  acid  are  brought,  the  nitric  acid  being  collected  in  large 
stoneware  bottles. 

Nitric  acid  thus  obtained  is  represented  by  the  formula  H 
NOa ;  it  is  a  strongly  fuming  liquid,  colorless  when  pure, 
but  usually  slightly  yellow  from  the  presence  of  lower  oxides 
of  nitrogen.  Its  specific  gravity  is  1-51  at  18°;  it  does  not 
possess  a  constant  boiling  point,  as  it  gradually  undergoes 
decomposition  by  boiling  and  becomes  weaker  :  if  mixed  with 
water,  and  distilled  under  the  ordinary  atmospheric  pressure, 
the  residual  acid  is  found  at  last  to  attain  a  fixed  composition, 
boiling  constantly  at  I2o°5,  containing  68  per  cent,  of  H  NOa, 
and  possessing  a  specific  gravity  of  r4H.  When  mixed  with 
less  water,  a  stronger  acid  than  this  comes  over  ;  when  mixed 
with  more  water,  a  weaker  one  distils  over  till  this  constant 
composition  is  attained.  Nitric  acid  contains  76  per  cent,  of 
oxygen,  with  some  of  which  it  easily  parts  ;  hence  it  acts  as  a 
strong  oxidizing  agent ;  this  is  seen  when  we  bring  a  small 
quantity  of  copper  or  tin  into  this  liquid  diluted  with  a  little 
water ;  red  fumes  are  immediately  given  off,  and  the  metals 
are  oxidized  ;  for  the  same  reason  nitric  acid  bleaches  indigo 
solution,  oxidizing,  and  therefore  destroying,  the  coloring 
matter :  this  reaction,  and  the  formation  of  red  fumes  in 
presence  of  metallic  copper,  &c.,  serve  as  modes  of  detecting 
the  presence  of  nitric  acid.  One  of  the  most  delicate  tests 
for  this  acid  consists  in  adding  to  the  liquid  to  be  tested  an 
equal  volume  of  strong  sulphuric  acid,  well  cooling  the  mixture, 
and  then  carefully  pouring  on  to  its  surface  a  solution  of 
ferrous  sulphate,  Fe  SO* :  a  black  ring  is  produced  where  the 
two  layers  of  liquid  meet  if  any  nitric  acid  be  present.  Nitric 
acid  forms,  with  metallic  oxides,  by  the  process  of  double 
decomposition,  a  numerous  family  of  salts  called  nitrates  : 
these  are  nearly  all  soluble  in  water,  and  many  of  them  are 
largely  used  in  the  arts  for  various  purposes.  They  will  be 
mentioned  under  the  several  metals. 


56  Elementary  Chemistry. 

Nitric  Pentoxide,  or  Nitric  Anhydride. — Symbol  N2  O5,  or 
J^Q*  (•  O.  This  oxide  of  nitrogen  cannot  be  prepared  directly 

from  liquid  nitric  acid  ;  but  if  dry  chlorine  gas  be  passed 
over  silver  nitrate,  silver  chloride  is  formed,  oxygen  is  given 
off,  and  a  white  crystalline  substance  produced,  which  on 
analysis  is  found  to  be  nitric  pentoxide.  The  decomposition 
is  thus  represented — 

2.  Ag  NO3  +  2  Cl.  =  N2O5  +  O  +  2  Ag  Cl. 
Nitric  Pentoxide  melts  at  +  30°  and  boils  at  +  45°  ;  it  very 
easily  undergoes  decomposition,  and  unites  with  great  energy 
with  water,  forming  nitric  acid  N2O5  +  H2O  =  2  NO3H  : 
this  may  be  represented  as  a  double  decomposition,  in  which 
one  atom  of  hydrogen  changes  place  with  NO2,  thus  : — 


N02  f  v      r  H 

The  fact  that  the  composition  of  nitric  pentoxide  is  repre 
sented  by  the  formula  N2O5,  may  be  ascertained  experiment 
ally  by  determining  the  quantity  of  nitrogen  contained  in  100 
parts  of  nitric  pentoxide,  which  is  first  converted  into  nitric 
acid  by  the  aid  of  water  as  above,  and  then  into  lead  nitrate 
by  treatment  with  lead  oxide,  thus  : — 

Pb,  O  +  2  N03H  =  Pb,  2  NO3  +  H2O. 

We  thus  find  the  nitrogen  to  weigh  25-93  parts,  and  hence 
the  oxygen  100-25-93,  or  74-07  parts.  We  then  wish  to  know 
what  is  the  simplest  relation  in  which  the  combining  weights 
of  nitrogen  and  oxygen  are  contained  in  this  compound  ;  in 
other  words,  what  is  the  ratio  of  the  number  of  atoms  of 
nitrogen  present  to  the  number  of  those  of  oxygen.  This  is 
ascertained  by  dividing  the  above  numbers  by  the  respective 
combining  weights  of  these  two  elements  ;  thus — 

5123  =,-852  and  ^=4-63  = 

hence  the  ratio  of  the  number  of  atoms  of  nitrogen  present  to 
the  number  of  atoms  of  oxygen,  is  that  of  the  numbers  i  -852  to 
4-6294,  or  that  of  2  to  4'999-  Hence  we  conclude  that  the 


Elementary  Chemistry. 


57 


exact  relation  between  the  number  of  atoms  of  nitrogen  and 
oxygen  respectively  is  that  of  2  to  5,  the  slight  difference 
which  is  noticed  being  due  to  the  unavoidable  errors  which 
accompany  every  experimental  inquiry,  and  are,  therefore, 
termed  errors  of  experiment.  All  the  other  oxides  of  nitrogen 
may  be  obtained  from  nitric  acid  by  depriving  it  of  its  hydro 
gen,  and  more  or  less  of  its  oxygen. 


LESSON  VII. 

Nitrous  Oxide,  or  Laughing  Gas. — Symbol  N2  O,  Combining 
Weight  44,  Density  22,  is  obtained  by  heating  ammonium 


NH4 


nitrate,  NH4  NO3   or  ^Q*  j.  O,  in  a  flask  such  as  that  used 

for  the  production  of  Qxygen,  and  is  best  collected  over  warm 
water  (see  Fig.   17).     The  salt  decomposes  on  heating,  into 


FIG.  17. 


nitrous  oxide  and  water:  NH4  NO3  =  N2O  +  2H2O  ;  or 
ammonium  nitrate  yields  nitrous  oxide  and  water.  Nitrous 
oxide  is  a  colorless  inodorous  gas  possessing  a  slightly  sweet 
taste ;  it  is  somewhat  soluble  in  cold  water,  one  volume  of 
water  at  o°  dissolving  1-305  volumes  of  the  gas,  whilst  one 

3* 


58  Elementary  Chemistry. 

volume  of  water  at  24°  dissolves  only  0*608  volume.  Nitrous 
oxide  differs  from  all  the  gases  which  we  have  previously 
considered,  inasmuch  as  it  liquifies  when  exposed  either  to 
great  pressure  or  to  an  intense  degree  of  cold.  Thus,  if  it  be 
brought  under  a  pressure  of  about  30  atmospheres  at  o°,  or  if 
it  be  cooled  down^to  -88°  under  the  ordinary  pressure,  it 
forms  a  colorless  liquid  (in  other  words  the  tension  of  nitrous 
oxide  vapor  or  gas  is  I  atmosphere  at  -88°,  and  30  atmos 
pheres  at  o°  C).  If  this  liquid  be  cooled  below  -115°  it 
solidifies  to  a  transparent  mass.  By  the  rapid  evaporation 
of  this  liquid  in  vacuo,  the  lowest  artificial  temperature 
hitherto  known  has  been  attained,  viz.,  about  -140°  C. 

A  glowing  chip  of  wood  when  plunged  into  nitrous  oxide 
rekindles,  and  the  wood  continues  to  burn  with  a  brighter 
flame  than  in  the  air,  whilst  phosphorus  on  burning  in  this 
gas  evolves  nearly  as  much  light  as  in  pure  oxygen  ;  a  feeble 


FIG.  1 8. 

flame  of  sulphur  is,  however,  extinguished  on  bringing  it 
into  this  gas,  but  if  burning  strongly  it  also  continues  to  burn 
brightly.  This  is  owing  to  the  fact  that  the  gas  has  to  be  de 
composed  into  nitrogen  (i  volume)  and  oxygen  (£  a  volume) 
before  bodies  can  burn  in  it ;  and  to  effect  this  decomposition 
a  tolerably  high  temperature  is  necessary,— the  same  products 
of  combustion  are  produced  as  if  the  combustion  went  on  in 
the  air.  When  inhaled,  nitrous  oxide  produces  a  peculiar  in 
toxicating  effect  on  the  human  frame  ;  hence  the  name  Laugh 
ing  gas.  The  composition  of  nitrous  oxide  may  be  determined 


Elementary  Chemistry.  59 

as  follows  :  a  bent  tube  (Fig.  18)  is  filled  with  the  dry  gas  over 
mercury  up  to  a  certain  mark  on  the  tube,  a  small  pellet  of 
metallic  potassium  having  been  previously  introduced  into  the 
bent  part  of  the  tube ;  this  is  then  heated  by  a  spirit  lamp,  or 
Bunsen's  burner,  while  the  open  end  of  the  tube  is  closed 
with  the  thumb  under  the  mercury,  to  prevent  a  loss  of  gas 
by  sudden  expansion  caused  by  the  combustion.  The  potas 
sium  burns  in  the  gas,  uniting  with  the  oxygen  to  form  solid 
potassium  oxide,  or  potash,  whilst  the  nitrogen  remains  in  the 
tube.  On  removing  the  thumb  and  allowing  the  tube  to  cool, 
it  will  be  seen  that  the  volume  of  nitrogen  is  exactly  the  same 
as  the  volume  of  nitrous  oxide  taken  ;  hence  this  gas  contains 
its  own  volume  of  nitrogen.  But  we  know  by  experiment 
that  the  weight  of  one  volume  of  the  gas  is  22,  so  that  if  we 
subtract  from  this  the  weight  of  one  volume  of  nitrogen  (viz. 
14)  we  shall  obtain  the  weight  of  oxygen  (8)  contained  in  one 
volume  of  nitrous  oxide.  Hence  we  see  that  two  volumes  of 
nitrous  oxide  are  composed  of  two  volumes  of  nitrogen  and 
one  volume  of  oxygen,  or  44  parts  by  weight  of  nitrous  oxide 
contain  28  of  nitrogen  and  16  of  oxygen.  The  specific  grav 
ity  of  nitrous  oxide  (air=  i)  is  i'S^7  •  1000  cbc.  at  o°  and  760 
mm.  weigh  1*972  grm. 

Nitric  Oxide. — Symbol  NO  ;  Combining  Proportion  30  ; 
Density  15  ;  a  colorless  gas  obtained  by  acting  upon  copper 
turnings  with  nitric  acid  thus: — 3  Cu. +  8  HNO3=3  (Cu. 
2  NO3)  +  2  NO +  4  H2O.  Copper  and  nitric  acid  give  copper 
nitrate,  nitric  oxide,  and  water. 

This  substance  has  not  been  condensed  to  a  liquid  ;  in  con 
tact  with  oxygen  it  combines  directly  with  this  latter  gas, 
forming  red  fumes  which  are  readily  soluble  in  water,  and  by 
this  property  it  may  be  distinguished  from  all  other  gases. 
Although  nitric  oxide  contains  half  its  volume  of  oxygen,  and 
more  oxygen  in  proportion  by  weight  than  nitrous  oxide,  it 
does  not  easily  support  combustion,  as  it  requires  a  high  tem 
perature  for  its  decomposition  ;  thus,  ignited  phosphorus,  un 
less  burning  very  brightly,  is  extinguished  on  plunging  it  into 
nitric  oxide  gas. 


60  Elementary  Chemistry. 

The  composition  of  this  gas  may  be  determined  according 
to  the  method  described  under  nitrous  oxide  ;  one  volume  of 
nitric  oxide  yields  \  a  volume  of  nitrogen  ;  as  the  weight  of 
one  volume  of  nitric  oxide  is  15,  the  weight  of  oxygen  con 
tained  in  one  volume  of  this  gas  is  15 — 7=8  :  or  two  volumes 
of  nitric  oxide  weigh  30,  and  are  composed  of  one  volume  of 
nitrogen  weighing  14,  and  one  of  oxygen  weighing  16.  Hence, 
in  accordance  with  the  law  mentioned  on  p.  27  respecting  the 
densities  of  compound  gases,  the  formula  of  nitric  oxide 
should  be  NO  and  not  N2O2:  the  physical  properties  of  the  gas 
likewise,  compared  with  those  of  nitrous  oxide,  seem  to  indi 
cate  that  this  latter  has  a  more  complicated  constitution  ;  thus 
nitric  oxide  has  not  as  yet  been  seen  in  the  liquid  form,  does 
not  condense  to  a  liquid  at  temperatures  and  pressures  at 
which  nitrous  oxide  readily  liquefies  ;  nitric  oxide  is  more 
difficultly  decomposed  by  heat  than  nitrous  oxide,  and  there 
fore  supports  combustion  less  easily ;  and  it  is  a  general  law 
that  in  a  series  of  similar  bodies  the  more  complicated  be  the 
constitution  of  one  member,  the  more  readily  does  it  con 
dense  to  the  liquid  form,  and  the  more  easily  does  it  decom 
pose. 

The  specific  gravity  of  nitric  oxide  (air  =  i)  is  1-038, 
and  1,000  cbc  of  this  gas  at  o°  and  760  mm.  weigh  1343 
grm. 

Nitric  Trioxide,  or  Nitrous  Anhydride. — Symbol  N2O3  ; 
Combining  Weight  76  ;  Density  38.  This  substance  is  pre 
pared  by  mixing  four  volumes  of  dry  nitric  oxide  with  one 
volume  of  oxygen,  and  cooling  the  mixture  to  — 18°  ;  the  two 
gases  combine  to  form  red  fumes,  which  condense  to  a  vola 
tile  indigo-blue  colored  liquid  ;  the  same  blue  body  is  ob 
tained  by  adding  water  to  nitric  tetroxide  and  drying  the  distil- 
jate  over  calcium  chloride.  When  mixed  with  water  nitric  triox- 
ide  decomposes,  nitric  oxide  and  nitric  acid  being  formed,  thus  : 

3  Na  O3  +  H2  O  =  2  H  N  O,  +  4  N  O. 

As  Nitric  Pentoxide  is  connected  with  a  series  of  salts 
called  Nitrates,  by  the  fact  that  all  these  salts  may  be  re- 


Elementary  Chemistry.  6 1 

presented  as  nitric  pentoxide,  in  which  one  of  the  groups 
NOa  has  been  replaced  by  a  metal,  thus  : 

Nitric  pentoxide    ^Q    j-  O  ;  potassium  nitrate  ^Q    (•  O  ; 
hydric  nitrate  1  O  ; 


so  also  is  nitric  trioxide  connected  with  a  parallel  series  of 
salts  called  Nitrites  j  thus  : 

"fa"("\  \  T£"       "\ 

Nitric  trioxide     NQ  [-  O  ;  potassium  nitrite    No  [•  O  ; 
>  u  ) 

H  ) 
hydric  nitrite  (unknown)  ^Q  j-    O.  .. 

As  Hydric  Nitrate  is  known  by  the  name  nitrzV  acid,  so 
Hydric  Nitrite  is  referred  to  as  niirous  acid ;  it  being  a  gen 
eral  rule  in  chemical  nomenclature  that  if  the  specific  name  of 
an  acid  or  hydrogen  salt  end  in  "  ous,"  the  names  of  the  cor 
responding  metallic  salts  end  in  "  ite  ;"  while  if  the  name  of 
the  acid  end  in  "  ic,"  the  names  of  the  corresponding  metallic 
salts  end  in  "ate;  "thus  nitric  acid  and  potassium  nitrate, 
nitrous  acid  and  potassium  nitrite,  are  respectively  analogous. 

Potassium  nitrite  K  NO2  is  obtained  by  heating  nitre  or 
potassium  nitrate  KNO3,  when  the  third  atom  of  oxygen  is 
evolved  ;  and  also  by  passing  N2O3  into  solutions  of  KHO. 

Nitric  Tetroxide,  or  Nitric  Peroxide. — Symbol  NO2,  Com 
bining  Weight  46,  Density  23.  This  substance  forms  the 
greater  part  of  the  reddish  brown  fumes  evolved  when  nitric 
oxide  gas  escapes  into  the  air ;  it  is  however  best  prepared 
by  heating  lead  nitrate  in  a  hard  glass  retort ;  lead  oxide, 
oxygen,  and  nitric  tetroxide  are  produced  by  the  decomposi 
tion  of  the  nitrate,  thus  : 

2  (Pb  2  N03)  =  2  PbO  +  4  NO2  +  02. 

Nitric  peroxide  NO2  solidifies  at  —  9°  to  long  prisms  ; 
these  on  fusing  yield  a  yellow  liquid,  boiling  at  22°.  Owing 
to  the  fact  that  the  density  of  nitric  tetroxide  is  23,  its  formula 
is  considered  to  be  NO2  and  not  N2  O*. 


62  Elementary  Chemistry. 

Compounds  of  Nitrogen  with  Hydrogen. 

But  one  is  as  yet  known  in  the  free  state,  viz.  : 
Ammonia.  —  Symbol  N  H3,  Combining  Weight  17,  Density 
8'5.  Nitrogen  and  hydrogen  do  not  readily  unite  when 
brought  together  alone,  but  do  so  under  certain  circum 
stances,  especially  when  water  is  evaporated  ;  the  nitrogen 
of  the  air  then  combines  with  the  elements  of  the  water, 
forming  small  quantities  of  the  compound  ammonium  nitrite 

Thus  N2  +  2H2O=N2H402,  or  NH4,  N  O2. 


Ammonia  is  chiefly  obtained  from  the  decomposition  of  animal 
or  vegetable  matter  containing  nitrogen  and  hydrogen,  being 
formed  either  gradually  at  the  ordinary  temperature,  or  quickly 
under  the  influence  of  heat  :  thus  when  horns,  or  clippings  of 
hides,  or  coal,  is  heated,  ammonia  is  given  off;  hence  ammo 
nia  was  known  as  spirits  of  hartshorn.  The  name  ammonia 
is  derived  from  the  fact  that  a  compound  containing  ammonia, 
called  salammoniac,  was  first  prepared  by  the  Arabs  in  the  de 
serts  of  Libya,  near  the  temple  of  Jupiter  Ammon,  by  heating 
camels'  dung.  Guano,  the  dried  excrement  of  sea  birds,  and 
the  urine  of  animals,  likewise  contain  large  quantities  of  am 
monia.  Ammonia  and  its  compounds  are  now,  however, 
mainly  obtained  from  the  ammoniacal  liquors  of  the  gas 
works  :  coal  contains  about  2  per  cent,  of  nitrogen,  which, 
when  the  coal  is  heated  in  close  vessels,  mostly  comes  oft  in 
combination  with  the  hydrogen  of  the  coal  as  ammonia.  Am 
monia  may  also  be  formed  by  the  action  of  nascent  hydrogen 
on  dilute  nitric  acid  ;  thus,  when  this  acid  is  placed  in  contact 
with  metallic  zinc  or  iron,  ammonia  is  formed,  thus  : 


Ammonia  gas  is  best  prepared  by  heating  in  a  glass  flask 
one  part  of  salammoniac,  or  ammonia  hydrochlorate,  NH3  H 
Cl  or  N  H4C1,  and  two  parts  of  powdered  quicklime,  thus 
CaO  +  2  NH3  HC1  =  CaCl2  +  2NH3  +  H2O. 

Quicklime  and  salammoniac  give  calcium  chloride,  and  am- 


Elementary  Chemistry.  63 

monia  and  water.  Ammoniacal  gas  is  colorless,  and  pos 
sesses  a  most  pungent  and  peculiar  smell,  by  means  of  which 
it  can  be  readily  recognized  ;  it  is  lighter  than  air,  its  specific 
gravity  (air=i)  being  0^59,  and  it  may  be  collected  by  displace 
ment,  the  neck  of  the  bottle  intended  to  receive  the  gas  being 
turned  downwards,  as  in  Fig.  19.  It  may  also  be  collected  over 


FIG.  19. 

mercury,  but  not  over  water,  as  it  is  extremely  soluble  in  this 
liquid,  one  gramme  of  water  at  o°  absorbing  0-877  grms->  or 
1149  times  its  volume  of  ammonia,  under  a  pressure  of  760 
mm.  ;  whilst  at  20°  the  same  weight  of  water  absorbs  0-520 
grin.,  or  68 1 '8  times  its  volume,  under  the  same  pressure. 
The  solution  of  ammonia  gas  in  water  is  the  common  Liquor 
Ammoniae  of  the  shops,  which  has  a  specific  gravity  of  about 
0-880.  Ammonia  gas,  as  well  as  the  aqueous  solution,  pos 
sesses  a  strong  alkaline  reaction,  turning  red  vegetable  colors 
blue  :  it  unites  with  the  most  powerful  acids,  forming  com 
pounds  called  the  Salts  of  Ammonia  (seep.  167),  which  closely 
resemble  the  salts  of  the  alkaline  metals  ;  hence  the  name  of 


64 


Elementary  Chemistry. 


the  Volatile  Alkali  has  been  given  to  Ammonia.     The  action 
of  ammonia  gas  on  nitric  acid  may  be  thus  represented  : 

'    NH3  +  NOsH=N03NH4  ;  or  ^4  j  O. 

Ammonia  gas  and  nitric  acid  give  ammonium  nitrate. 

On  exposure  to  a  pressure  of  seven  atmospheres  at  the  or 
dinary  temperature  of  the  air  (about  15°  C),  ammonia  con 
denses  to  a  colorless  liquid,  boiling  at  —38-5°  ;  and  this 
liquid,  if  cooled  below  -75°,  freezes  to  a  transparent  solid  ;  it 
has  at  o°  the  specific  gravity  0-62.  An  elegant  application  of 
the  principle  of  the  latent  heat  of  vapors  has  recently  been 
made  in  the  case  of  ammonia  in  M.  Carry's  freezing  machine, 


FIG.  20. 

Fig.  20.  This  consists  essentially  of  two  strong  iron  vessels 
connected  in  a  perfectly  air-tight  manner  by  a  bent  pipe  ;  one 
of  these  vessels  contains  an  aqueous  solution  of  ammonia 
saturated  with  the  gas  at  o°.  When  it  is  desired  to  procure 
ice,  the  vessel  A  containing  the  ammonia  solution  (which  we 
will  term  the  retort)  is  gradually  heated  over  a  large  gas 
burner,  the  other  vessel  B  (the  receiver)  being  placed  in  a 
bucket  of  cold  water  :  in  consequence  of  the  increase  of  tem 
perature,  the  gas  cannot  remain  dissolved  in  the  water,  and 


Elementary  Chemistry,  65 

passes  into  the  receiver,  where,  as  soon  as  the  pressure 
amounts  to  about  10  atmospheres,  it  condenses  in  the  liquid 
form.  When  the  greater  part  of  the  gas  has  thus  been  driven 
out  of  the  water,  the  apparatus  is  reversed,  the  retort  (A) 
being  cooled  in  a  current  of  cold  water,  whilst  the  liquid  it  is 
desired  to  freeze  is  placed  in  the  interior  of  the  receiver 
(B).  A  re-absorption  of  the  ammonia  by  the  water  now  takes 
place,  and  a  consequent  evaporation  of  the  liquefied  ammonia 
in  the  receiver  ;  this  evaporation  is  accompanied  by  an  ab 
sorption  of  heat,  which  becomes  latent  in  the  gas  ;  hence  the 
receiver  is  soon  cooled  far  below  the  freezing  point,  and  ice  is 
produced  around  it. 

The  composition  of  ammonia  may  be  ascertained  by  lead 
ing  the  gas  through  a  red-hot  tube,  or  passing  a  series  of  elec 
tric  sparks  through  the  gas,  when  it  will  be  decomposed  into 
nitrogen  and  hydrogen,  which  will  be  found  to  occupy  together 
a  volume  twice  as  large  as  the  ammonia  taken,  and  to  be  mixed 
together  in  the  proportions  of  three  volumes  of  hydrogen  to 
one  volume  of  nitrogen.  Hence  the  formula  N  H3  is  given  to 
the  gas. 

The  Salts  of  Ammonia  will  be  described  together  with  those 
of  Potassium  and  Sodium  (page  167).  The  compound  ammo 
nias  will  be  noticed  under  Organic  Chemistry. 


LESSON  VIII. 

CARBON.     Symbol  C.     Combining  Weight  1 2. 

Carbon  is  the  first  solid  element  which  we  have  to  notice  ; 
it  is  not  known  in  the  free  state,  either  as  a  liquid  or  as  a  gas. 
Carbon  is  remarkable  as  existing  in  three  distinct  forms, 
which,  in  outward  appearance  or  physical  properties,  have 
nothing  in  common,  whilst  their  chemical  relations  are  ident 
ical.  These  three  allotropic  forms  of  carbon  are  (i)  Diamond, 


66  Elementary  CJicmistry. 

(2)  Graphite  or  Plumbago,  (3)  Charcoal:  these  substances 
differ  in  hardness,  color,  specific  gravity,  £c.,  but  they  each 
yield,  on  combustion  in  the  air  or  oxygen,  the  same  weight  of 
the  same  substance,  Carbonic  Acid,  or  carbon  di-oxide;* 
12  parts  by  weight  of  each  of  these  forms  of  carbon  yielding 
44  parts  by  weight  of  carbon  di-oxide.  Carbon  is  the  element 
which  is  specially  characteristic  of  animal  and  vegetable  life, 
as  every  organized  structure,  from  the  simplest  to  the  most 
complicated,  contains  carbon  :  if  carbon  were  not  present  on 
the  earth,  no  single  vegetable  or  animal  body  such  as  we  now 
know  could  exist.  In  addition  to  the  carbon  which  is  found 
free  in  these  three  forms,  and  that  contained  combined  with 
hydrogen  and  oxygen  in  the  bodies  of  plants  and  animals,  it 
exists  combined  with  oxygen  as  free  carbonic  di-oxide  in  the 
air,  and  with  calcium  and  oxygen  as  calcium  carbonate  in 
limestone,  chalk,  marble,  corals,  shells,  &c.  The  fact  has 
already  been  noticed  that  plants  are  able,  when  exposed  to 
sunlight,  to  decompose  the  carbonic  di-oxide  of  the  air,  liberat 
ing  the  oxygen,  and  taking  the  carbon  for  the  formation  of 
their  vegetable  structure,  whilst  all  animals  living  directly  or 
indirectly  upon  vegetables  absorb  oxygen,  and  evolved  car 
bonic  di-oxide.  Thus  the  sun's  rays,  through  the  medium  of 
plants,  effect  deoxidation  or  reduction,  while  animals  act  as 
oxidizing  agents  with  respect  to  carbon. 

The  element  carbon  not  only  combines  directly  with  oxy 
gen,  but  also  with  hydrogqi,  forming  a  compound  called  Ace 
tylene,  C2H2.  Carbon  forms  with  oxygen,  hydrogen,  and 
nitrogen  a  series  of  more  or  less  complicated  compounds 
very  much  more  extended  than  the  series  formed  with  these 
bodies  by  any  other  element ;  so  that  these  compounds  are 
considered  as  a  separate  branch  of  the  science  under  the 
name  of  Organic  Chemistry,  or  the  CJicmistry  of  the  Carbon 
Compounds.  The  properties  of  the  majority  of  these  com 
pounds  will  be  examined  in  a  subsequent  chapter,  owing 

*  Although  the  term  Acid  strictly  denotes  a  hydrogen  salt,  yet  the  word  has  been 
applied  so  long  to  a  few  other  compounds  containing  no  hydrogen,  such  as  carbon 
di-oxide,  &c.,  that  these  bodies  are  universally  known  by  the  names  carbonic  acid,  &c. 


Elementary  Chemistry,  67 

to  their  complexity ;  hence  till  then  it  will  be  better  to 
postpone  the  consideration  of  several  of  the  properties  of 
carbon. 

The  Diamond  was  first  found  to  consist  of  pure  carbon  by 
Lavoisier,  in  1775-6,  by  burning  it  in  oxygen,  and  collecting 
the  carbon  di-oxide  formed ;  it  occurs  crystallized  in  certain 
sedimentary  rocks  and  gravel  in  India  (Golconda),  Borneo, 
_and  the  Brazils.  Diamond  occurs  crystallized  in  forms  (Fig. 
21),  derived  by  a  symmetrical  geometric  operation  from  a  re 
gular  Octahedron,  known  as  belonging  to  the  regular  system 


of  Crystallography  (see  p.  150).  The  specific  gravity  of  Dia 
mond  varies  from  3-3  to  3-5  ;  it  is  the  hardest  of  all  known 
bodies,  and  when  cut  possesses  a  brilliant  lustre,  and  a  high 
refractive  power.  In  addition  to  .-its  employment  as  a  gem, 
the  diamond  is  used  for  cutting  and  writing  upon  glass.  We 
are  altogether  unacquainted  with  the  mode  in  which  the  dia 
mond  has  been  formed  ;  it  cannot,  however,  have  been  pro 
duced  at  a  high  temperature,  because  when  heated  strongly 
in  a  medium  incapable  of  acting  chemically  upon  it,  the  dia 
mond  swells  up,  and  is  converted  into  a  black  mass  resembling 
coke. 

Graphite,  or  Plumbago,  crystallizes  in  six-sided  plates 
which  have  no  relation  to  the  form  in  which  the  diamond  crys 
tallizes.  Graphite  occurs  in  the  oldest  sedimentary  forma 
tions,  and  in  granitic  or  primitive  rocks  :  it  is  found  in  Bor- 


68  Elementary  Chemistry. 

rowdale  in  Cumberland,  and  in  large  quantities  in  Siberia  and 
Ceylon.  It  has  a  black  metallic  appearance  (whence  the 
familiar  name  black  lead),  and  leaves  a  mark  when  drawn 
upon  paper.  The  specific  gravity  of  graphite  is  2*15  to  2-35. 
Coarse  impure  graphite  may  be  purified  by  heating  the  powder 
with  sulphuric  acid  and  potassium  chlorate  ;  a  compound  is 
thus  obtained  which,  on  being  heated  strongly,  decomposes, 
leaving  pure  graphite  in  a  bulky  and  finely-divided  powder : 
this  powder  when  strongly  compressed  forms  a  coherent 
mass,  from  which  pencils  and  other  articles  can  be  made. 
Graphite  is  used  for  polishing  surfaces  of  iron-work,  and  also 
for  giving  a  protecting  varnish  to  grains  of  gunpowder.  Gra 
phite  is  produced  in  the  manufacture  of  iron ;  it  occa 
sionally  separates  from  the  molten  pig-iron  in  the  form  of 
scales. 

Charcoal  is  the  third  allotropic  modification  of  carbon.  It 
is  obtained  in  a  more  or  less  pure  state  whenever  animal  or 
vegetable  matter  is  heated  to  redness  in  a  vessel  nearly 
closed  ;  the  volatile  matters  (compounds  of  carbon,  hydrogen, 
and  oxygen)  are  thus  driven  off,  and  the  residue  of  the  carbon, 
together  with  the  ash  or  mineral  portion  of  the  organism,  re 
mains  behind. 

The  purest  form  of  charcoal  carbon  is  found  in  lampblack  ; 
it  also  occurs  as  wood  charcoal,  coal,  coke,  and  animal  char 
coal.  This  form  of  carbon  does  not  crystallize,  and  is  hence 
termed  amorphous  ;  it  is  much  lighter  than  either  of  the  other 
two  forms,  the  specific  gravity  of  powdered  coke  varying  from 
1-6  to  2-0.  Charcoal  appears  at  first  sight  to  be  lighter  than 
water,  as  a  piece  of  it  floats  on  the  surface  of  this  liquid  ;  this 
is,  however,  due  to  the  porous  nature  of  the  charcoal,  for  if  it 
be  finely  powdered  it  sinks  to  the  bottom  of  the  water.  This 
porous  nature  of  charcoal  enables  it  to  exert  a  remarkable 
absorptive  power,  of  which  much  use  is  made  in  the  arts. 
Charcoal  is  thus  able  to  absorb  about  ninety  times  its  own 
volume  of  ammonia  gas,  and  about  nine  volumes  of  oxygen. 
In  the  process  of  sugar-refining,  use  is  made  of  the  property 
of  charcoal  to  absorb  the  coloring  matters  present  in  the  raw 


Elementary  Chemistry. 


sugar:  the  kind  of  charcoal  best  suited  to  this  purpose  is  that 
obtained  by  heating  bones  in  a  closed  vessel.  Charcoal  is 
also  used  as  a  disinfectant  in  hospitals  and  dissecting  rooms, 
&c.  It  appears  that  the  putrefactive  gases  when  absorbed  by 
the  charcoal  undergo  a  gradual  oxidation  from  contact  with 
the  oxygen  of  the  air  taken  up  by  the  charcoal,  and  are  thus 
rendered  harmless. 

Coal  is  a  form  of  carbon  less  pure  than  wood  charcoal. 
It  consists  of  the  remains  of  a  vegetable  world  which  once 
flourished  on  the  earth's  surface  :  the  original  woody  fibre  has 
undergone  a  remarkable  transformation  in  passing  into  coal, 
having  been  subjected  to  a  process  similar,  in  a  chemical 
point  of  view,  to  that  by  which  wood  is  transformed  into 

Composition  of  Fuels  (ash  being  deducted). 


Percentage  Composition. 

Description  of  Fuel. 

Carbon. 

Hydrogen. 

Nitrogen 

[and  Oxygen. 

I  Woodv  Fibre       .... 

52*6  f! 

C  2C 

42"IO 

2  Peat  from  the  Shannon    . 

60  '02 

5'88 

34-10 

3  Lignite  from  Cologne  .     . 
4  Earthy  Coal  from  Dax 

66-96 

74-20 

5-25 
5-89 

2776 
19-90 

5  Wigan  Cannel     .... 

85-81 

585 

8'34 

6  Newcastle  Hartley  .     .     . 

88-42 

56l 

5'97 

7  Welsh  Anthracite   .     .     . 

94-05 

3-38 

2-57 

charcoal.  It  has  not,  however,  lost  the  whole  of  its  hydrogen 
and  oxygen,  and  it  has  at  the  same  time  become  bitumenized  ; 
so  that  for  the  most  part  all  the  vegetable  structure  has  dis 
appeared.  There  are  many  different  kinds  of  coal,  containing 
more  or  less  of  the  oxygen  and  hydrogen  of  the  original  wood  : 
cannel  coal  and  boghead  coal  contain  the  most  hydrogen,  and 
anthracite  coal  the  least.  The  alteration  in  composition  which 
wood  has  undergone  in  passing  into  the  various  forms  of  coal 
is  seen  from  the  above  table. 


/O  Elementary  Chemistry. 


Compounds  of  Carbon  with  Oxygen. 

Carbon  forms  two  compounds  with  oxygen,  viz. : 
Carbonic  Oxide,  or  C  O. 
Carbonic  Dioxide,  or  C  O2 

Carbonic  Dioxide,  or  Carbonic  Acid.  Symbol  C  Oa,  Com 
bining  Weight  44,  Density  22. 

Carbonic  dioxide  is  always  formed  when  carbon  is  burnt  in 
excess  of  air  or  oxygen.  It  is  best  prepared  by  acting  upon 
marble,  chalk,  or  other  form  of  calcium  carbonate,  with  hydro 
chloric  acid.  On  pouring  some  of  this  acid  upon  pieces  of 
marble  contained  together  with  some  water  in  a  flask,  a  rapid 
effervescence  from  the  disengagement  of  carbonic  dioxide  gas 
at  once  occurs,  calcium  chloride  being  left  behind  in  solution 
in  the  flask  :  the  decomposition  is  thus  represented  : 
Ca  C03  +  2HC1  =  CO2  +  H20  +  Ca  Cla. 

Calcium  carbonate  and  hydrochloric  acid  give  carbonic 
dioxide,  water,  and  calcium  chloride. 

Carbonic  dioxide  occurs  free  in  the  air,  and  in  the  water  of 
many  mineral  springs.  The  quantity  of  this  gas  present  in 
the  air  is  nearly  constant,  and  amounts  to  about  4  volumes  per 
10,000  of  air;  this  quantity,  though  relatively  small,  is,  taken 
altogether,  very  large,  being  about  3  billions  of  tons  in  weight, 
as  can  be  easily  calculated  if  we  know  the  weight  of  the 
atmosphere  and  the  density  of  carbonic  acid. 

Owing  to  the  evolution  of  carbonic  dioxide  in  respiration 
and  in  the  burning  of  coal-gas,  &c.,  this  gas  is  always  found 
in  larger  quantities  in  dwelling-rooms  than  in  the  open  air. 
When  the  air  of  a  room  contains  o*ro  per  cent,  of  this  gas  it 
is  certainly  unfit  for  continued  respiration,  not  only  on  accoun 
of  the  deleterious  effects  produced  by  carbonic  dioxide,  but 
also  because,  together  with  this  gas,  volatile  putrescible  mat 
ters  are  given  off  from  the  skin  and  lungs  of  animals,  and  these 
matters  act  in  a  prejudicial  manner  upon  the  health ;  hence 
the  necessity  for  attention  to  the  ventilation  of  dwelling-rooms 
and  public  buildings.  Carbonic  dioxide  gas  is  also  given  off 


Elementary  Chemistry.  71 

in  the  process  of  fermentation  ;  it  occurs  frequently  at  the 
bottom  of  old  wells,  and  forms  the  chokedamp  of  the  coal 
mines.  Compounds  containing  calcium  and  magnesium,  &c., 
and  bearing  a  peculiar  relation  to  carbonic  dioxide,  such  as 

limestone  or  calcium  carbonate,  ^^  >•  Oa,  magnesian  limestone, 

&c.,  occur  plentifully  in  nature,  sometimes  forming  whole 
mountain  chains.  Calcium  carbonate  also  constitutes  the 
main  portion  of  coral,  a  substance  of  which  whole  continents 
are  being  built  up  in  the  Pacific  Ocean. 

Carbonic  dioxide  gas  is  colorless  and  inodorous,  but  pos 
sesses  a  slightly  acid  taste  ;  it  is  1*529  times  heavier  than  air, 
and  is  tolerably  soluble  in  water,  one  volume  of  water  at  o° 
dissolving  1797  volumes  of  this  gas,  whilst  at  20°  only  0-901 
volumes  is  absorbed.  The  volume  of  this  gas  absorbed  by 
water  at  the  same  temperature  is  found  to  remain  the  same, 
whatever  the  density  of  the  gas  may  be,  —  that  is,  howsoever 
the  pressure  may  vary  under  which  the  gas  is  placed  (the 
measurements  of  the  volumes  absorbed  being  made  under 
these  different  pressures).  As  the  volumes  occupied  by  any 
given  quantity  of  gas  measured  under  different  pressures  vary 
inversely  as  these  pressures,  it  is  clear  that  the  weights  of  gas 
thus  absorbed  must  be  proportional  to  the  pressures.  The 
same  relation  is  found  to  hold  good  when  many  other  gases 
are  dissolved  in  water  under  varying  pressures. 

The  aqueous  solution  of  carbonic  dioxide  reddens  blue 
litmus  paper,  and  when  placed  in  contact  with  a  metallic  oxide, 
such  as  calcium  oxide  or  lime,  CaO,  gives  rise  to  the  forma 
tion  of  salts  such  as  calcium  carbonate  :  this  aqueous  solution 
may  be  considered  to  contain  a  true  acid,  the  real  carbonic 

H    ) 

acid,  ^Q  J-  O2  (which,  however,  has  never  yet  been  isolated), 

and  the  reaction  which  then  takes  place  may  be  thus  repre 
sented  : 

02  +  Ca  O  =    C      02  +  H20. 


Carbonic  acid  and  calcium  oxide  give  calcium  carbonate 


72  Elementary  Chemistry. 

and  water.  The  red  color  produced  by  the  acid  on  litmus 
paper  disappears  on  drying,  owing  to  the  decomposition  of  this 
true  carbonic  acid  into  carbonic  dioxide  and  water,  thus  : 

02  =  C02  +  H20. 

Carbonic  dioxide  can  be  condensed  to  a  liquid  by  the  appli 
cation  of  great  pressure,  or  by  cooling  the  gas  to  a  very  low 
temperature :  liquid  carbonic  dioxide  is  a  colorless  and  very 
mobile  liquid,  which  is  remarkable  as  being  found  to  expand 
by  heat  more  than  the  gaseous  form  of  the  same  substance, 
100  volumes  of  this  liquid  at  o°  becoming  106  volumes  at  10°, 
while  100  volumes  of  the  gas  at  o°  must  be  heated  to  16-4° 
before  they  expand  to  106  volumes  ;  hence  this  body  is  an 
exception  to  the  rule  that  liquids  expand  by  heat  less  than 
gases,  and  at*  the  same  time  forming  an  excellent  illustration 
of  the  fact,  that  liquids  expand  proportionally  much  more 
when  submitted  to  a  high  pressure  than  when  under  a 
low  one  ;  thus,  the  expansion  of  water  above  100°  is  much 
greater  than  that  below  100°.  The  boiling  point  of  carbonic 
dioxide  is  -78°.  At  a  still  lower  temperature  it  freezes  to  a 
colorless,  ice-like  solid.  At  o°  the  tension  of  its  vapor  is 
35-5  atmospheres  ;  and,  at  30°,  73-5  atmospheres.  The  lique 
faction  of  carbonic  dioxide  gas  can  be  effected  either  by  evolv 
ing  the  gas  in  a  strong  closed  vessel,  so  that  it  is  condensed 
by  its  own  pressure,  or  by  pumping  the  gas  by  means  of  an 
ordinary  forcing  syringe  into  a  strong  wrought-iron  receiver, 
kept  during  the  process  at  a  temperature  of  o°.  As  soon  as 
the  volume  of  gas  pumped  in  amounts  to  about  36  times  the 
volume  of  the  receiver,  each  stroke  of  the  syringe  produces  a 
condensation  of  the  gas  which  is  pumped  in,  and  thus  the 
receiver  can  easily  be  filled  with  liquid.  If  the  stopcock  be 
then  opened  so  that  the  liquid  is  forced  out,  a  portion  at  once 
assumes  the  gaseous  state  ;  and  so  much  heat  is  absorbed  by 
this  sudden  transition  from  the  liquid  to  the  gaseous  form,  that 
a  portion  of  the  liquid  is  solidified  and  deposited  in  the  form 
of  white,  snow-like  flakes,  which  can  be  collected  by  allowing 
the  stream  of  liquid  to  flow  into  a  thin  brass  box,  with  per- 


Elementary  Chemistry. 


73 


forated  sides.  Solid  carbonic  dioxide  thus  obtained,  is  a  light, 
snow-like  substance,  which,  owing  to  the  bad  conducting 
power  for  heat  of  the  gas  which  the  solid  substance  is  con 
stantly  giving  off,  may  be  handled  without  damage,  although 
its  temperature  is  below  -78°  C.  If, 
however,  the  solid  be  forcibly  pressed 
between  the  fingers,  so  that  the  sub 
stance  really  comes  in  contact  with 
the  skin,  a  sharp  pain  will  be  felt,  and 
a  blister  like  one  produced  by  touch 
ing  a  hot  iron  will  be  produced.  This 
solid  carbonic  dioxide  is  much  used 
for  the  production  of  very  low  tem 
peratures  ;  for  this  purpose  it  is 
mixed  with  ether,  and  the  mixture 
brought  into  the  vacuum  of  the  air- 
pump,  whereby  a  temperature  as  low 
as  -100°  C.  can  be  obtained,  and 
large  quantities  of  mercury  may  eas 
ily  be  frozen.  Carbonic  dioxide  gas 
does  not  support  the  combustion  of 
bodies  in  general,  such  as  wood, 
sulphur  or  phosphorus  ;  but  certain 
metals — for  instance,  potassium  and 
magnesium — heated  in  the  gas,  are 
able  to  decompose  it,  burning  in  it, 
and  uniting  with  the  oxygen  to  form 
oxides,  while  the  carbon  is  liberated. 
The  composition  of  carbonic  diox 
ide  may  be  ascertained  with  great  ex 
actness  by  burning  a  known  weight  of 
pure  carbon,  such  as  the  diamond,  in 
a  current  of  pure  oxygen  gas,  and 
weighing  the  carbonic  dioxide  pro 
duced.  The  apparatus  for  this  synthesis  of  this  gas  is  repre 
sented  in  Fig.  22.  The  weighed  quantity  of  diamond  placed  in 
a  small  platinum  boat,  is  pushed  into  the  porcelain  tube,  which 

4 


74  Elementary  Chemistry. 

can  be  strongly  heated  in  the  furnace.  One  end  of  this  tube 
is  connected  with  a  gasholder  and  drying  tubes,  A,  B,  C,  by 
means  of  which  pure  and  dry  oxygen  gas  is  supplied.  The 
other  end  is  connected,  as  is  seen,  with  a  number  of  tubes 
and  bulbs  destined  to  absorb  the  carbonic  dioxide  formed 
by  the  combustion  ;  the  tube  D  and  the  bulbs  E  contain 
solution  of  caustic  potash,  and  the  other  tubes  F  are  filled 
with  pumice-stone  and  sulphuric  acid.  The  bulbs  and  tubes 
are  carefully  weighed,  and  then  the  apparatus  is  filled  with 
pure  oxygen,  and  the  tube  slowly  brought  to  a  red  heat. 
The  gas  passes  gradually  through  the  system  of  tubes,  and 
carries  along  with  it  the  carbonic  dioxide  formed  by  the 
combustion  of  the  diamond  :  this  gas  is  wholly  absorbed 
by  the  potash  in  the  tube  and  bulbs,  whilst  any  moisture 
which  might  be  given  off  from  the  bulbs  is  taken  up  by 
the  tubes  F.  The  oxygen  gas  is  dried  as  it  enters  and  also 
as  it  leaves  the  apparatus  ;  so  that  the  gain  in  weight  which 
the  tubes  have  experienced  gives  exactly  the  weight  of  car 
bonic  dioxide  formed  by  the  combustion  of  the  carbon  of  the 
diamond.  Usually  the  diamond  contains  a  small  quantity  of 
ash,  or  inorganic  matter,  and  this  weight  must  be  subtracted 
from  the  original  weight  of  the  diamond,  in  order  that  we  may 
know  the  exact  weight  of  pure  carbon  burnt  ;  for  this  reason 
the  diamond  is  placed  in  a  platinum  boat,  which  can  be  with 
drawn  and  weighed  after  the  experiment,  and  thus  the  amount 
of  ash  determined.  Another  precaution  that  must  be  taken 
is,  to  fill  the  greater  part  of  the  red-hot  tube  with  porous  cop 
per  oxide,  in  case  any  trace  of  carbonic  oxide  gas  (C  O)  should 
be  formed  by  the  incomplete  combustion  of  the  carbon  ;  this 
gas  would  pass  unabsorbed  through  the  potash  if  not  oxidized 
to  carbonic  dioxide  by  the  copper  oxide.  In  this  way  it  has 
been  shown  that  100  parts  of  carbonic  dioxide  consist  of 

Carbon 27*27 

Oxygen 7273 

Carbonic  dioxide     .     .  loo'oo 


Elementary  Chemistry.  75 

If  we  divide  27*27  by  the  combining  weight  of  carbon,  and 

7273  by  that  of  oxygen,  we  have  =2-273  and  — ^- = 

4-545  ;  or,  the  relation  between  the  number  of  atoms  of  car 
bon  and  that  of  those  of  oxygen  is  that  of  i  to  2  ;  hence  the 
formula  of  carbonic  dioxide  is  C  O2.  Hence  the  gas  should 
contain  its  own  volume  of  oxygen  ;  for  44  parts  by  weight  of 
carbonic  dioxide  occupying  a  volume  equal  to  that  occupied 
by  2  parts  by  weight  of  hydrogen,  contain  32  parts  by  weight 
of  oxygen,  which  likewise  occupy  a  volume  equal  to  that  of  2 
parts  of  hydrogen.  That  this  is  the  case  can  be  experiment 
ally  proved  by  burning  charcoal  in  a  known  volume  of  oxygen 
in  excess,  when  it  is  observed  that  when  the  gas  has  cooled 
after  the  combustion,  no  alteration  in  its  volume  has  occurred  ; 
hence  the  volume  of  carbonic  dioxide  formed  must  be  precisely 
equal  to  that  of  the  oxygen  used  in  its  formation. 

r.i  P>  R  A  it  v 

i  UNJ  V  KKS1TV   () 

LESSON  IX.     (!AL1F()R> 

CARBONIC    OXIDE.      Symbol   CO.     Combining    Weight  28. 
Density  14. 

When  carbon  burns  with  a  limited  supply  of  oxygen,  car 
bonic  oxide  is  formed.  The  production  of  this  gas  in  an 
ordinary  red-hot  coal  fire  is  often  observed  ;  oxygen  of  the 
air,  which  enters  at  the  bottom  of  the  grate,  combines  with 
the  carbon  of  the  coal,  forming  carbonic  dioxide  ;  this  sub 
stance  then  passing  upwards  over  the  red-hot  coals,  parts 
with  half  its  oxygen  to  the  red-hot  carbon  ;  thus  : — 

CO,  +  C  =  2  CO. 

This  carbonic  oxide  on  coming  out  at  the  top  of  the  fire 
meets  with  atmospheric  oxygen,  with  which  it  at  once  com 
bines,  burning  with  a  lambent  blue  flame,  and  reforming  car- 


76  Elementary  Chemistry. 

bonic  dioxide.  Carbonic  oxide  gas  in  the  pure  state  can  be 
prepared  by  passing  a  slow  current  of  carbonic  oxide  over 
pieces  of  charcoal  heated  to  redness  in  a  tube  by  means  of  a 
furnace,  as  represented  in  Fig.  23  :  it  may  likewise  be  ob 
tained  in  the  pure  state  from  several  compounds  of  carbon. 
Thus,  if  crystallized  oxalic  acid  be  heated  with  strong  sul 
phuric  acid,  a  mixture  of  equal  volumes  of  carbonic  oxide  and 
carbonic  dioxide  gases  is  evolved  ;  this  latter  can  be  easily 
separated  from  the  former  by  shaking  the  mixed  gas  up  with 
caustic  soda  solution,  when  sodium  carbonate  will  be  formed, 


FIG.  23. 

half  the  volume  of  the  gas  will  disappear,  and  the  remainder 
will  be  found  to  be  pure  carbonic  oxide.  This  decomposition 
of  oxalic  acid  results  from  the  fact  that  sulphuric  acid  has  a 
strong  tendency  to  abstract  water,  or  the  elements  of  water, 
from  the  bodies  with  which  it  comes  into  contact ;  thus  the 
oxalic  acid,  which  may  be  represented  as  C2  H2  O4  (see  p. 
289),  being  deprived  of  the  elements  of  one  molecule  of  water, 
which  are  taken  up  by  the  sulphuric  acid,  yields  a  compound, 
Ca  O3,  which  cannot  exist  alone,  and  immediately  splits  up 
into  COa  and  CO. 

Carbonic  oxide  can  also  be  prepared  by  heating  Formic 
acid,  C  H2  O3  (see  p.  271),  with  sulphuric  acid  :  here,  as  with 
oxalic  acid,  the  elements  of  water  are  removed,  and  pure  CO 


Elementary  Chemistry.  77 

is  thus  evolved.  Carbonic  oxide  is  a  colorless,  tasteless  gas, 
which  has  not  been  condensed  to  a  liquid  ;  it  is  a  little  lighter 
than  air,  its  specific  gravity  being  0-969  (air  =  i  )  :  it  is  but 
very  slightly  soluble  in  water.  It  acts  as  a  strong  poison, 
producing  death  when  inhaled  even  in  very  small  quantities, 
the  fatal  effects  often  observed  of  the  fumes  from  burning 
charcoal,  or  from  limekilns,  being  due  to  the  presence  of  car 
bonic  oxide.  When  heated  in  contact  with  oxygen,  carbonic 
oxide  takes  fire,  burning  with  a  characteristic  lambent  blue 
flame  and  forming  carbonic  dioxide.  In  contact  with  caustic 
potash  at  a  high  temperature,  carbonic  oxide  produces  potas 
sium  formate  thus : 

H  >  ^  +  CO  =  CHKO2. 


Caustic  potash  and  carbonic  oxide  give  potassium  formate. 

The  composition  of  this  gas  can  be  ascertained  by  combus 
tion  in  the  Eudiometer  with  oxygen.  100  volumes  of  car 
bonic  oxide  and  75  volumes  of  oxygen  yield  on  passing  the 
electric  spark  125  volumes,  of  which  100  are  found  to  be 
absorbed  by  caustic  potash,  and  hence  are  carbonic  dioxide, 
the  remaining  25  volumes  being  unaltered  oxygen.  Hence 
the  volume  of  carbonic  dioxide  produced  is  equal  to  that  of 
the  carbonic  oxide  taken,  whilst  the  volume  of  oxygen  needed 
is  half  as  large.  But  as  carbonic  dioxide  contains  its  own 
volume  of  oxygen,  carbonic  oxide  must  contain  half  its  vofume 
of  oxygen  ;  or  two  volumes  of  this  gas  weighing  28  contain 
one  volume  of  oxygen  weighing  16,  and  hence  12  parts  of 
carbon  by  weight :  therefore  its  formula  is  CO. 

Compounds  of  Carbon  with  Hydrogen, 

These  compounds  are  very  numerous  ;  they  are  known  in 
the  gaseous,  liquid,  and  solid  forms.  The  most  important  and 
numerous  parts  of  these  will  be  considered  under  Organic 
Chemistry ;  we  have  only  now  to  speak  of  two,  viz  : 

Light,  carburet  ted  hydrogen,  CH4 

Heavy  carburetted  hydrogen,  C2H4. 


78  Elementary  Chemistry. 

Methyl  Hydride,  Light  Carburetted  Hydrogen,  or  Marsh 
gas.  Symbol  CH4  ;  Combining  Weight  16,  Density  8. 

This  is  a  colorless,  tasteless,  inodorous  gas,  which  has 
not  been  condensed  to  a  liquid.  It  is  found  in  coal  mines, 
and  known  under  the  name  of  fi  redamp  ;  it  also  occurs  in 
stagnant  pools,  being  produced  by  the  decomposition  of  dead 
leaves,  whence  the  name  marsh  gas  ;  it  is  one  of  the  con 
stituents  of  coal  gas,  £c.,  and  is  evolved  in  many  volcanic 
districts.  Marsh  gas  may  also  be  artificially  prepared  by  heat 
ing  sodium  acetate  (see  p.  275)  with  caustic  soda,  thus  : 

Na  H  Na2  H 


4.  O 

C2H30         +Na}0=  CO 

Sodium  acetate  and  caustic  soda  give  sodium  carbonate 
and  marsh  gas. 

Marsh  gas  burns  with  a  bluish-yellow  non-luminous  flame, 
forming  carbonic  dioxide  and  water  ;  with  a  limited  supply  of 
air  it  yields  several  products,  amongst  which  is  acetylene, 
C2H2.  If  mixed  with  ten  times  its  volume  of  air,  and  twice 
its  volume  of  oxygen,  it  ignites  with  a  sudden  and  violent 
explosion  on  the  application  of  a  light,  and  hence  the  great 
damage  produced  by  the  escape  of  this  gas  in  coal  mines. 
The  composition  of  marsh  gas  is  ascertained  by  exploding  it 
with  oxygen  in  the  eudiometer  ;  I  volume  of  this  gas  and  3 
volumes  of  oxygen  yield  2  volumes  after  passage  of  the  spark. 
On  absorbing  by  potash  the  carbonic  dioxide  produced,  I 
volume  of  oxygen  is  found  to  remain.  Hence  of  the  2  volumes 
of  oxygen  needed  to  burn  the  I  volume  of  marsh  gas,  I  has 
gone  to  unite  with  the  carbon,  and  I  to  form  water  with  the 
hydrogen.  It  is  thus  seen  that  2  volumes  of  marsh  gas  con 
tain  4  volumes  of  hydrogen  weighing  4  (as  water  contains  2 
volumes  of  hydrogen  and  I  of  oxygen),  and  as  much  carbon 
as  is  contained  in  2  volumes  of  carbonic  dioxide,  viz.,  12 
parts  by  weight  :  and  hence  the  formula  CH4  is  given  to  this 
gas. 

Ethylene,  Heavy  Carburetted  Hydrogen  or  Olejiant  Gas. 
Symbol  C2  H4,  Combining  Weight  28,  Density  14. 

This  gas  is  obtained  on  the  destructive  distillation  of  coal, 


Elementary  Chemistry.  79 

and  is  an  important  constituent  of  coal  gas.  It  is  obtained  in 
the  pure  state  by  heating  i  part  of  alcohol  (spirits  of  wine) 
C2  H6  O,  with  5  or  6  parts  by  weight  of  strong  sulphuric  acid  ; 
as  in  formation  of  carbonic  oxide  from  formic  acid,  the  ele 
ments  of  water  are  separated  by  the  sulphuric  acid,  and  C2H4 
is  evolved  as  a  gas.  This  gas  is  colorless,  but  possesses  a 
sweetish  taste  ;  by  exposure  to  a  high  pressure  at  a  tempera 
ture  of — 110°  it  has  been  condensed  to  a  colorless  liquid. 
On  bringing  it  in  contact  with  a  light,  in  the  air,  it  burns  with 
a  luminous  smoky  flame,  forming  carbonic  dioxide  and  water. 
When  mixed  with  three  times  its  bulk  of  oxygen  and  fired,  it 
detonates  very  powerfully  ;  i  volume  of  olefiant  gas  requires 
3  volumes  of  oxygen  to  burn  it  completely,  and  yields  2. 
volumes  of  carbonic  dioxide  ;  so  that  i  volume  of  oxygen  is 
needed  to  combine  with  the  hydrogen.  Hence  this  gas  con 
tains  twice  as  much  carbon  as  marsh  gas,  with  the  same 
quantity  of  hydrogen  ;  we  must  therefore  write  its  formula 
C3H4.' 

Olefiant  gas  combines  directly  with  its  own  volume  of 
chlorine  gas,  forming  an  oily  liquid,  and  owing  to  this  prop 
erty  it  has  received  the  above  name. 

Coal  Gas. 

The  gas  so  largely  used  for  illuminating  purposes,  and  ob 
tained  by  the  destructive  distillation  of  coal  (/.  e.  by  heating 
the  coal  in  large  closed  retorts  so  as  to  decompose  or  destroy 
the  coal,  the  volatile  products  of  this  decomposition  being 
condensed  and  collected),  is  not  a  simple  chemical  compound, 
but  a  mixture  of  a  large  number  of  distinct  substances.  In 
order  to  prepare  coal  gas  of  good  quality,  cannel,  or  some 
highly  bitumenized  coal  is  heated  in  a  closed  retort ;  volatile 
bodies  are  thus  formed  and  expelled,  while  a  residue  of  (im 
pure)  carbon  is  left  behind  as  coke.  The  volatile  products  of 
this  decomposition  may  be  distinguished  as  tar,  ammonia, 
water,  and  gas.  The  tar  contains  a  great  variety  of  sub- 


So 


Elementary  Chemistry. 


stances,  from  some  of  which  the  well-known  Aniline  colors 
are  produced  (see  p.  322) ;  and  the  ammonia  derived  from  the 
nitrogen  in  the  coal  is  our  chief  source  of  ammoniacal  salts 
(see  p.  174).  The  gas  which  comes  off  consists  of  a  mixture 
of  various  substances,  some  of  which  are  useful  for  illuminat 
ing  or  heating  purposes,  whilst  some  are  hurtful  and  must  be 
removed.  Amongst  those  which  burn  with  a  luminous  flame, 
are  olefiant  gas,  and  other  hydrocarbons  having  an  analogous 
composition,  as  Ca  H6  and  C4  H8  (where  the  number  of  atoms 
of  hydrogen  is  double  that  of  those  of  carbon).  The  gases 
which  serve  to  dilute  these  luminous  hydrocarbons,  and  burn 
themselves  with  non-luminous  flames,  are  hydrogen,  carbonic, 
oxide,  and  marsh  gas.  The  impurities  consist  of  carbonic 
dioxide,  hydric  sulphide  (sulphuretted  hydrogen),  and  the  va 
por  of  carbon  di-sulphide  ;  and  these  substances  are  almost 
always  withdrawn  from  the  gas  by  a  system  of  purification  be 
fore  it  is  sent  out  from  the  gasworks.  The  relative  propor 
tion  of  these  three  ingredients  present  in  coal  gas  varies 
greatly  according  to  the  kind  of  coal  employed,  and  according 
to  the  heat  to  which  the  coal  is  subjected.  This  is  seen  from 
the  following  table,  in  which  the  composition  of  a  gas  made 
from  common  coal  with  that  of  one  made  from  cannel  is 
given  : 


Illumi 

COMPOSITION  IN  100  VOLUMES. 

nating 

power  :  . 

Candles 
per  5 
cubic 

Hydro 
gen. 

Marsh 
Gas. 

Heavy 
Hydro- 

carbons. 

Equal  to 
Olefiant 
Gas. 

Carbonic 
Oxide. 

Nitrogen, 
Oxygen, 
and 
Carbonic 

feet. 

Acid. 

Cannel  Gas. 

34'4 

25-82 

51'20 

13-06 

(22'OS) 

7-35 

2.07 

Coal  Gas.... 

13-0 

47-60 

4I-53 

3-05 

(    6-97) 

7-82 

— 

The  value  of  coal  gas,  as  regards  its  illuminating  power,  is 
ascertained  by  comparing  the  light  given  off  by  the  gas  burn 
ing  at  a  certain  rate,  usually  5  cubic  feet  per  hour,  with  that 


Elementary  Chemistry. 


81 


of  a  sperm  candle  burning  120  grains  per  hour.  Thus  the 
cannel  gas  is  said  to  be  equal  to  34-4  candles,  and  the  coal 
gas  to  be  equal  to  13  candles. 

It  will  be  convenient  here  to  mention  the  nature  and  struc 
ture  of  flame,  and  the  principle  of  the  Davy  lamp.  Flame 
consists  of  gas  in  a  high  state  of  ignition.  When  a  jet  of 
burning  hydrogen  is  plunged  into  oxygen,  the  flame  of  hydro 
gen  in  oxygen  is  seen.  This  is  caused  by  the  ignition  of  the 
particles  of  hydrogen  and  oxygen,  owing  to  the  heat  evolved 
in  their  combination.  A  similar  flame  of  oxygen  in  hydrogen 
is  seen  when  a  jet  of  the  former  gas  is  lit  in  an  atmosphere  of 
hydrogen.  The  temperatures  of  flames  differ  as  much  as 
their  illuminating  powers,  and  the  hottest  flames  do  not  neces 
sarily  give  off  much  light ;  thus  the  oxyhydrogen  flame,  which 
is  so  hot  as  to  burn  iron  or  steel  wire  like  tinder,  can  scarcely 
be  seen  in  bright  daylight.  In  order  that  a  flame  shall  give 
off  much  light,  it  must  contain  solid  matter,  which  becomes 
heated  up  to  whiteness.  If  a  piece  of 
lime  be  held  in  the  oxyhydrogen  flame, 
it  becomes  strongly  heated,  and  gives 
off  an  intense  light ;  so  also  if  we  bring 
solid  matter,  such  as  powdered  charcoal, 
into  the  colorless  flame  of  hydrogen,  it 
becomes  luminous.  The  difference  be 
tween  the  non-luminous  flame  of  marsh 
gas  and  the  luminous  flame  of  olefiant 
gas  is  due  to  the  fact  that  in  the  latter, 
carbon  is  separated  out  in  the  solid  form, 
whereas  in  the  former  all  the  carbon  is 
at  once  burnt  to  a  carbonic  acid.  The 
flame  of  a  candle  consists  of  three  dis 
tinct  parts — (i),  the  dark  central  zone  or 
supply  of  unburnt  gas  surrounding  the 
wick ;  (2),  the  luminous  zone  or  area  of  incomplete  combus 
tion;  and  (3),  the  non-luminous  zone  or  area  of  complete  com 
bustion.  If  we  bring  one  end  of  a  small  piece  of  glass  tubing 

(Fig.  24)  into  the  dark  central  zone  (i),  the  unburnt  gases  will 
4* 


FIG.  24. 


82  Elementary  Chemistry. 

pass  up  the  tube,  and  may  be  ignited  at  the  other  end,  where 
they  escape  into  the  air.  In  the  luminous  part  of  the  flame 
the  gases  are  not  completely  burnt,  and  carbon  is  separated 
out  in  the  solid  state  ;  and  it  is  to  the  presence  of  this  car 
bon  that  the  flame  owes  its  luminous  power.  In  the  outer 
zone  the  supply  of  oxygen  is  greater,  all  the  carbon  is  at  once 
burnt  to  carbonic  acid,  and  the  flame  here  becomes  non- 
luminous.* 

The  effect  of  allowing  a  complete  combustion  to  proceed  at 
once  throughout  the  flame  is  well  seen  in  the  small  Bunsen 
gas-lamp,  now  universally  employed  in  laboratories.  In  this 
lamp  (Fig.  25)  the  coal  gas  issues  from  a  small  central  burner 
(a),  and  passing  unburnt  up  the  tube  (e)  draws  air  up  with  it 
through  the  holes  (d) ;  the  mixture  of  air  and  gas  thus  made 
can  be  lighted  at  the  top  of  the  tube,  where  it  burns  with  a 


FIG.  25.  FIG.  26. 

non-luminous,  perfectly  smokeless  flame  ;  if  the  holes  (d)  be 
closed,  the  gas  alone  burns  with  the  ordinary  bright  smoky 
flame.  The  blow-pipe  flame  (Fig.  26)  may  also  be  divided 
into  two  distinct  parts — the  oxidizing  flame  (a),  where  there 
is  excess  of  oxygen,  and  the  reducing  flame,  (ff)  where  there 
is  excess  of  carbon  ;  and  these  are  distinguished  by  the  same 

*  The  optical  difference  between  these  two  classes  of  flame  is  pointed  out  in  the 
paragraph  on  Spectrum  Analysis,  (see  p.  222.) 


Elementary  Chemistry.  83 

properties  as  the  outer  and  inner  mantle  of  the  candle  flame. 
Every  mixture  of  gases  requires  a  certain  temperature  to  in 
flame  it ;  and  if  the  temperature  be  not  reached,  the  mixture 
does  not  take  fire  ;  we  may  thus  cool  down  a  flame  so  much 
that  it  goes  out,  by  placing  over  it  a  small  coil  of  cold  copper 
wire,  whereas,  if  the  coil  be  previously  heated,  the  flame  will 
continue  to  burn.  The  same  fact  is  well  shown  with  a  piece 
of  wire  gauze  containing  about  700  meshes  to  the  square  inch  : 
*:f  this  be  held  close  over  a  jet  of  gas,  and  the  gas  lit,  it  is  pos 
sible  to  remove  the  gauze  several  inches  above  the  jet,  and 
yet  the  inflammable  gas  below  does  not  take  fire,  the  flame 
burning  only  above  the  gauze  (Fig.  27).  The  metallic  wires 
in  this  case  so  quickly  conduct  away  the  heat  that  the  tem 
perature  of  the  gas  at  the  lower  side  of  the  gauze  cannot  rise  to 
the  point  of  ignition.  This  simple  principle  was  made  use  of  by 
Sir  Humphry  Davy  in  his  safety-lamp  for  coal  mines.  It  con 
sists  of  an  oil  lamp  (Fig.  28),  the  top  of  which  is  inclosed  in  a 


FIG.  27.  FIG.  28. 

covering  of  wire  gauze  ;  the  air  can  enter  through  the  meshes 
of  the  gauze,  and  the  products  of  combustion  of  the  oil  can  es 
cape,  but  no  flame  can  pass  from  the  inside  to  the  outside  of 
the  gauze.;  and  hence,  even  if  the  lamp  be  placed  in  a  most  in 
flammable  mixture  of  fire-damp  and  air,  no  ignition  is  possi- 


84  Elementary  Chemistry. 

ble,  although  the  combustible  gas  may  take  fire  and  burn  in 
side  the  gauze.  It  is,  however,  then  advisable  that  the  miner 
should  withdraw,  to  avoid  risk  of  explosion  of  the  gas  from 
the  gauze  thus  becoming  overheated  and  inflaming  the  fire 
damp  which  surrounds  it.  The  compounds  of  carbon  being 
generally  of  a  more  complicated  nature  than  the  preceding 
ones,  they  will  be  more  completely  considered  under  the  head 
of  Organic  Chemistry. 


Compounds  of  Carbon  and  Nitrogen. 

One  only  is  known,  viz.  : 

Cyanogen.  Symbol  CN.  Combining  Weight  26.  Den 
sity  26. 

When  carbon  and  nitrogen  are  heated  together  in  presence 
of  potash,  a  remarkable  compound,  termed  Potassium  Cyanide, 
KCN,  is  formed.  From  this  substance  a  large  number  of 
bodies  can  be  prepared,  all  of  which  contain  the  group  of 
atoms  CN,  and  possess  characteristic  and  peculiar  properties  ; 
to  this  group  the  name  Cyanogen  is  given,  from  its  forming  a 
number  of  blue  compounds  (XWM/OJ  blue,  and  yt  rmw,  I  produce). 
Cyanogen  combines  with  metals  to  form  Cyanides,  and  in  this 
respect  resembles  chlorine. 

CN  )  * 
Gaseous  Cyanogen   -      \    can    be    easily    obtained    as    a 


colorless  gas  by  heating  mercuric  cyanide.  It  is  best  col 
lected  over  mercury,  as  it  is  soluble  in  water.  It  condenses 
to  a  colorless  liquid  when  exposed  to  a  pressure  of  about 
four  atmospheres  ;  it  is  inflammable,  and  burns  with  a  beauti 
ful  purple  flame,  forming  carbonic  acid  (dioxide  CO2)  and  free 
nitrogen.  Cyanogen  compounds  are  prepared  on  a  large 
scale  for  various  purposes  by  heating  nitrogenous  organic 
matter,  such  as  clippings  of  hides,  hoofs,  &c.  ;  with  iron  and 
potashes,  a  double  cyanide  containing  iron  and  potassium, 

*  The  reason  for  giving  the  double  formula  to  gaseous  cyanogen  will  be  explained 
further  on. 


Elementary  Chemistry.  85 

called  Potassium  Ferrocyanide,  or  yellow  Prussiate  of  Potash 
(see  Organic  Chemistry,  p.  298),  is  formed. 

Cyanogen  forms  with  hydrogen  a  compound  analogous  in 
composition  to  hydrochloric  acid  HC1,  and  called  Hydrocyanic 
Acid,  or  commonly,  Prussic  Acid,  HCN.  This  important 
substance  is  prepared  by  acting  on  potassium  cyanide  with 
dilute  sulphuric  acid  in  a  retort.  Hydrocyanic  acid  mixed 
with  water  distils  over,  leaving  potassium  sulphate  in  the 
retort,  thus  : 

2  KCN  +  H2SO4  =  K2SO4  +  2  HCN. 

It  is  prepared  pure  and  free  from  water  by  passing  sul 
phuretted  hydrogen  gas,  H2  S,  over  dry  mercuric  cyanide, 
hydrocyanic  acid,  and  mercurous  sulphide  being  formed, 
thus  : 

2  Hg  CN  +  H2S  =  2  (HCN)  +  Hg2S. 

Mercuric  cyanide  and  sulphuretted  hydrogen  yield  hydro 
cyanic  acid  and  mercurous  sulphide.  Hydrocyanic  acid  thus 
prepared  is  a  volatile  liquid,  boiling  at  26*5°,  and  solidifying 
at —  15°;  it  is  the  most  poisonous  substance  known,  one 
drop  of  the  pure  substance  being  sufficient  to  produce  fatal 
results  ;  much  care  must  therefore  be  taken  in  its  preparation 
not  to  inhale  the  vapor  which,  even  in  small  quantity,  may 
produce  death.  It  possesses  a  peculiar  and  characteristic 
smell  of  bitter  almonds,  and  occurs  in  small  quantities  in  the 
kernels  and  leaves  of  many  plants. 

Cyanogen  forms  a  large  number  of  compounds,  some  of 
them  of  a  very  complicated  constitution,  and  connected  with 
other  carbon  compounds,  under  which  they  \jrill  be  qonsidered. 

I  1MM,. 

"      '    '-'V,;,,,S,TV   Q 

LESSON  X.  A  L|  /«Y  H( 

We  now  pass  to  the  consideration  of  a  group  of  elements 
which  resemble  each  other  closely,  and  possess  sjrongly- 


86  Elementary  Chemistry. 

marked  and  active  properties  :  viz.  Chlorine,  Bromine,  Iodine, 
and  Fluorine. 


CHLORINE.     Symbol  Cl.     Combining  Weight  35-5. 
Density  35-5. 

Chlorine  was  discovered  in  the  year  1774  by  Scheele  :  it 
does  not  occur  free  in  nature,  but  can  easily  be  prepared 
from  its  compounds.  It  is  found  combined  with  metals  form 
ing  chlorides  ;  of  these  sodium  chloride,  sea  or  rock-salt,  is 
the  most  common :  to  obtain  chlorine  from  this,  it  must  be 
heated  with  sulphuric  acid  and  manganese  dioxide,  thus  : 
2  NaCl  +  2  SO4  Ha  +  MnO2  =  2  Cl  +  Na2  SO4  +  MnSO4 

+  2H.O. 

Sodium  chloride,  sulphuric  acid,  and  manganese  dioxide, 
give  chlorine,  sodium  sulphate,  manganese  sulphate,  and 
water. 

If  one  part  of  salt  to  one  part  of  manganese  dioxide  be 
mixed  with  two  parts  of  sulphuric  acid  and  two  of  water,  and 
the  mixture  brought  into  a  large  flask,  the  chlorine  gas  is 
given  off  regularly  upon  the  application  of  a  very  slight  heat ; 
in  order  to  obtain  the  gas  pure,  it  may  be  passed  through  the 
water  contained  in  a  wash-bottle  before  it  is  collected  for  use. 
Chlorine  is  a  green-yellow  gas,  possessing  a  most  disagreeable 
and  peculiar  smell,  which,  when  the  gas  is  present  in  small 
traces  only,  resembles  that  of  seaweed,  but  when  present  in 
large  quantities  acts  as  a  violent  irritant,  producing  inflamma 
tion  of  the  mucous  membrane,  and  even  causing  death  when 
inhaled.  Chlorine  gas  when  submitted  to  a  pressure  of  five 
atmospheres  at  the  ordinary  temperature,  is  condensed  to  a 
heavy  yellow  liquid,  but  it  has  not  yet  been  solidified.  This 
gas  cannot  be  collected  orer  water  or  mercury,  as  it  is  soluble 
in  the  former  (r  volume  of  water  dissolving  2*37  volumes  of 
chlorine  at  15°),  and  combines  directly  with  the  latter,  forming 
mercuric  chloride.  It  can,  however,  be  easily  collected  by 
displacement,  as  it  is  nearly  2-5  times  as  heavy  as  air.  If 


Elementary-  Chemistry.  87 

metals  in  a  freely  divided  state  are  brought  into  chlorine  gas, 
they  take  fire  spontaneously,  forming  metallic  chlorides : 
thus  powdered  arsenic,  antimony,  or  thin  copper  leaf,  burn 
when  thrown  into  the  gas. 

The  most  remarkable  property  of  chlorine  is  its  power  of 
combining  with  hydrogen  to  form  hydrochloric  acid  :  when 
these  two  gases  are  brought  together  in  equal  volumes,  they 
combine  with  explosion  on  bringing  a  flame  into  contact  with 
them,  or  on  exposing  the  mixture  to  sunlight.  Chlorine  is 
even  able  to  decompose  water  in  the  sunlight,  combining  with 
the  hydrogen  and  liberating  the  oxygen.  Several  experiments 
illustrative  of  this  property  of  chlorine  may  be  mentioned  :  if 
a  burning  candle  be  plunged  into  this  gas,  the  taper  continues 
to  burn,  but  with  a  very  smoky  flame,  the  hydrogen  alone  of 
the  wax  entering  into  combination  with  the  chlorine,  whilst 
the  carbon  is  given  off  as  smoke  or  soot :  the  same  eifect  is 
produced  when  a  paper  moistened  with  turpentine  (a  com 
pound  of  carbon  and  hydrogen)  is  held  in  a  jar  of  chlorine 
gas  ;  the  hydrogen  of  the  turpentine  at  once  combines  with 
the  chlorine,  forming  hydrochloric  acid,  and  the  carbon  is 
liberated  ;  so  much  heat  is  given  off  by  this  action  that  the 
paper  frequently  takes  fire. 

The  well-known  bleaching  action  of  chlorine  also  depends 
upon  its  power  of  combining  with  the  hydrogen  of  water  and 
liberating  the  oxygen.  Dry  chlorine  gas  does  not  bleach  ; 
we  may  inclose  a  piece  of  cotton  cloth  or  paper  colored  by  a 
vegetable  substance,  as  madder  or  litmus,  in  a  bottle  of  dry 
chlorine,  and  no  change  of  color  takes  place,  even  after  the 
lapse  of  many  weeks  :  if,  however,  a  few  drops  of  water  are 
added,  the  coloring  matter  is  immediately  destroyed,  and  the 
cotton  or  paper  is  bleached.  Here  the  chlorine  combines  with 
the  hydrogen  of  the  water,  and  the  oxygen  at  the  moment  of 
its  liberation  (when  it  is  said  to  be  nascent}  combines  with  the 
vegetable  coloring  matters,  forming  compounds  destitute  of 
color.  Ordinary  free  oxygen  has  not  this  power — not  at  least 
to  any  great  extent ;  it  is  a  frequent  observation  that  bodies 
in  this  nascent  state  have  more  active  properties  than  the 


88  Elementary  Chemistry. 

same  bodies  when  free  and  alone.  Chlorine  is  unable  to 
bleach  mineral  colors  ;  the  difference  between  printer's  ink, 
colored  by  lampblack  or  carbon,  and  writing  ink,  a  vegetable 
black,  is  well  illustrated  by  placing  a  sheet  of  paper  having 
characters  written  and  printed  upon  it  in  a  solution  of  chlorine 
in  water.  Chlorine  gas  is  largely  used  for  bleaching  purposes 
in  the  cotton,  linen,  and  paper  manufactures.  It  is  sometimes 
used  in  the  form  of  a  gas,  but  more  usually  in  combination 
with  calcium  and  oxygen,  forming  the  article  called  chloride 
of  lime  (mixture  of  calcium  chloride,  CaCl2,  and  calcium  hypo- 
chlorite,  CaCl2O2)  or  Bleaching  Powder.  Chlorine  is  also 
largely  employed  as  a  disinfectant  and  deodorant,  its  action 
on  organic  putrefactive  substances  being  similar  to  that  upon 
organic  coloring  matters. 


Compounds  of  Chlorine  with  Hydrogen. 

One  only  is  known,  viz  : — 

Hydrochloric    Acid,    or   Hydric    Chloride.      Symbol     HC1. 
Combining  Weight  36*5.    Density  18.25. 

This  substance  is  obtained  when  equal  volumes  of  chlorine 
and  hydrogen  are  mixed  and  exposed  to  the  diffused  light  of 
day  ;  the  gases  then  combine,  and  form  an  unaltered  volume 
of  hydrochloric  acid  gas.  If  the  light  be  strong,  this  combi 
nation  takes  place  so  rapidly  that  a  violent  explosion  occurs. 
Hydrochloric  Acid  may,  however,  be  more  easily  prepared  by 
heating  common  salt  (sodium  chloride)  and  sulphuric  acid  in 
a  flask. 

NaCl  +  So4  H2  =  HC1  +  Na  H  So4. 

Sodium  chloride  and  sulphuric  acid  give  hydrochloric  acid 
and  hydric  sodium  sulphate. 

Hydrochloric  Acid  is  a  colorless  gas  1*269  times  heavier 
than  air  ;  it  fumes  strongly  in  damp  air,  combining  with  the 
moisture,  and  has  a  strongly  acid  reaction.  It  is  very  soluble 
in  water,  one  volume  of  this  liquid  at  15°  dissolving  454 


Elementary  Chemistry.  89 

volumes  of  the  gas  ;  this  solution  is  the  ordinary  Hydro 
chloric  or  Muriatic  Acid  of  the  shops.  Under  a  pressure  of 
40  ats.  the  gas  forms  a  limpid  liquid.  The  gas  can  be  col 
lected  over  mercury,  and  its  solubility  in  water  strikingly 
shown  by  allowing  a  few  drops  of  water  to  ascend  to  the  sur 
face  of  the  mercury  in  contact  with  the  gas  :  a  rapid  rise  of 
the  mercury  in  the  jar  immediately  occurs.  A  saturated  solu 
tion  of  hydrochloric  acid  in  water  has  the  specific  gravity  of 
1-2 1  ;  it  fumes  strongly  in  the  air,  and  when  heated  in  a  re 
tort,  loses  at  first  hydrochloric  acid  gas,  but  after  a  time  an 
aqueous  acid  distils  over  at  the  ordinary  atmospheric  pres 
sure,  containing  20-22  per  cent,  of  HC1,  and  boiling  constant 
ly  at  1 10°.  If  the  distillation  be  conducted  under  a  diminished 
pressure,  the  acid  boils  constantly  at  a  lower  temperature, 
and  attains  a  composition  which  is  different  for  each  boiling 
point ;  hence  the  constant  acids  thus  obtained  by  boiling  the 
solution  of  hydrochloric  acid  gas  in  water  cannot  be  con 
sidered  as  definite  compounds  of  HC1  and  water.  This  fact 
holds  good  for  many  other  aqueous  solutions  of  acids,  &c., 
viz. :  that  residues  constantly  boiling  at  the  same  tempera 
ture,  and  having  constant  compositions,  are  obtained  on  dis 
tillation,  the  composition  and  boiling  point  varying,  however, 
with  the  pressure  under  which  the  distillation  has  been  con 
ducted. 

Enormous  quantities  of  Hydric  Chloride  (commonly  called 
Muriatic  Acid,  from  muria  sea-salt)  are  obtained  as  a  bye- 
product  in  the  manufacture  of  sodium  carbonate  (see  p.  162). 
More  than  1,000  tons  of  this  acid  are  made  every  week  in  the 
South  Lancashire  district  alone.  The  acid  thus  produced  is, 
however,  very  impure,  having  a  yellow  color,  and  contain 
ing  iron,  arsenic,  organic  matter,  and  sulphuric  acid  in  solu 
tion. 

The  arrangement  represented  in  Fig.  29  is  adapted  to 
show,  that  when  gaseous  hydric  chloride  is  passed  over 
heated  manganese  dioxide,  water  and  chlorine  gas  are  formed, 
thus: 

4  HC1  +  MnOa  =  Cla  +  2(H2O)  +  MnQ2. 


90  Elementary  Chemistry. 

If  the  gas  is  allowed  to  pass  over  the  oxide  contained  in 
the  first  bulb  before  it  is  heated,  no  formation  of  water  is 
noticed,  and  the  red  litmus  paper  in  the  bottle  remains 
colored  ;  as  soon  as  the  oxide  is  heated,  moisture  is  at  once 
seen  to  be  deposited  in  the  second  bulb,  and  the  paper  be 
comes  bleached,  showing  the  presence  of  chlorine.  The 
exact  composition  of  hydric  chloride  is  best  determined  by 
decomposing  the  aqueous  acid  by  means  of  a  current  of 
voltaic  electricity,  by  an  arrangement  similar  to  that  shown 


FIG.  29. 

in  Fig.  n,  and  collecting  the  gases  (hydrogen  and  chlorine) 
evolved  in  a  long  tube  after  allowing  the  decomposition  to  go 
on  for  some  time.  If  the  tube  thus  filled  be  opened  in  the 
dark  under  a  solution  of  potassium  iodide,  the  solution  will 
rise  in  the  tube,  the  iodine  being  liberated,  the  chlorine  com 
bining  with  the  potassium,  until  exactly  half  the  tube  is  filled 
with  liquid  ;  the  remaining  gas  is  found  to  consist  of  hydrogen. 
If  the  mixture  of  electrolytic  gases,  which  can  with  care  be 
sealed  up  in  a  strong  tube,  be  exposed  to  the  action  of  day 
light,  or  of  a  bright  artificial  light,  immediate  combination  of 
the  two  gases  will  ensue,  and  on  opening  the  tube  under  water, 
this  liquid  will  completely  fill  the  whole  of  the  tube,  showing 
that  the  component  gases  were  present  in  exactly  the  propor 
tion  needed  to  form  hydrochloric  acid. 


Elementary  Chemistry.  91 


Compounds  of  Chlorine  with  Oxygen. 

Chlorine  and  Oxygen  do  not  unite  directly,  but  they  may 
indirectly  be  made  to  form  the  following  compounds,  viz  :  — 

Compounds  of  Chlorine  and  Oxygen.  Corresponding  Acids. 


(2)  Chloric  Tri-oxide,  Cl2  C%  yielding  .  dr^cdorite  HC1°' 

(3)  Chloric  Tetroxide,  Cl-2  O*     .     .    .        No  corresponding  Acid  is  known. 

(4)  No  corresponding  Oxide  is  known  .  \  jgf^j  CMorte  \  HC1°3 


(5)  No  corresponding  Oxide  is  known  .  HC1O* 


The  oxides  C12O6  and  C12O7,  corresponding  respectively  to 
the  two  last  acids,  have  not  yet  been  prepared  in  the  free 
state. 

Hypochlorous  Oxide.  Symbol  Q  (  O,  or  C12O.     Combining 
Weight  87.     Density  43-5. 

This  body  is  obtained  by  the  action  of  chlorine  upon  mer 
curic  oxide  —  the  chlorine  combining  not  only  with  the  metal, 
but  also  with  the  oxygen,  thus  : 

Hg  O  +  2  C12  =  C12O  +  Hg  Cla. 

Mercuric  oxide,  and  chlorine,  give  hypochlorous  oxide,  and 
mercuric  chloride. 

It  is  a  colorless  gas,  which  may  be  condensed  by  means  of 
a  freezing  mixture  to  a  red  liquid,  which  is  very  explosive. 
It  is  soluble  in  water,  forming  a  solution  of  hypochlorous 
acid,  thus  H2O  +  C12O  =  2  HC1O  :  this  action  of  water  upon 
an  oxide,  forming  a  hydric  salt  or  acid,  is  a  very  general 
reaction  ;  it  occurred  with  nitric  pentoxide  N2O5  (N2O5  4- 
H3O  =  2  NO3H,  page  56),  and  with  carbonic  dioxide  (CO2  -f 
H2O  =  H2CO3.  page  72),  and  we  shall  frequently  meet  with 
it  hereafter. 


92  Elementary  Chemistry. 

Hypochlorous    Acid,    or    Hydric    Hypochlorite.       Symbol 

HC1O.     Combining  Weight  52-5. 

This  body  may  be  obtained  in  solution  in  water  by  dis 
tilling  dilute  solutions  of  sodium  hypochlorite  or  calcium 
hypochlorite  with  dilute  nitric  acid.  Thus  : 

Na  CIO  +  HNO3  =  Na  NO3  +  H  CIO. 

Sodium  hypochlorite  and  nitric  acid  give  sodium  nitrate 
and  hypochlorous  acid. 

It  may  be  regarded  as  hypochlorous  oxide  in  which  one 
atom  of  chlorine  has  been  replaced  by  one  of  hydrogen. 
When  this  atom  of  chlorine  is  replaced  by  metals,  a  series  of 
salts  called  Hypochlorites  is  obtained.  These  are  formed 
(together  with  chlorides)  whenever  chlorine  gas  acts  upon  the 
solution  of  certain  metajlic  oxides  in  water,  or  on  the  damp 
solid  oxides.  Thus  when  chlorine  acts  upon  moist  slaked 
lime,  bleaching  powder  (a  mixture  of  calcium  hypochlorite 
and  chloride)  is  produced  ;  the  reaction  may  be  explained 
thus  : 

2  Ca  H2O2  +  2  C12  =  2  H2  O  +  Ca  Clfl  +  Ca  C12  O2. 

Calcium  hydrate  and  chlorine  give  water,  calcium  chloride, 
and  calcium  hypochlorite. 

This  substance,  so  largely  used  for  bleaching  purposes,  is 
prepared  on  the  large  scale  by  passing  chlorine  gas  into 
spacious  chambers,  on  the  floors  of  which  a  layer  of  slaked 
lime  two  inches  thick  is  laid  ;  the  gas  is  all  absorbed,  and 
bleaching  powder  formed.  When  treated  with  a  small  quan 
tity  of  a  dilute  acid,  hypochlorous  acid  is  liberated,  and  may 
be  distilled  over,  whereby  an  aqueous  solution  is  obtained  as 
a  colorless  liquid,  having  a  peculiar  smell  and  bleaching  prop 
erties.  If  a  larger  quantity  of  acid  be  added,  the  hypochlor 
ous  acid  itself  is  decomposed  into  chlorine  and  water,  or 
hydrochloric  acid  and  oxygen.  Hence  in  the  operation  of 
bleaching,  the  goods  are  first  dipped  into  a  solution  of  bleach 
ing  powder,  and  then  passed  through  a  dilute  acid,  whereby 
hypochlorous  acid  is  first  formed  and  then  decomposed, 
liberating  chlorine  in  the  fibre  of  the  cloth  ;  the  bleaching 


Elementary  Chemistry.  93 

effect  is,  therefore,  only  visible  after  the  goods  have  been 
"  soured,"  or  dipped  in  the  acid. 

Chloric  Trioxide,  Symbol  C12O3,  is  produced  by  the  deoxi- 
dation  of  chloric  acid,  HC1O3  ;  it  is  connected  with  a  series 
of  salts  called  chlorites,  just  as  hypochlorous  oxide  is  with 
the  hypochlorites  ;  thus,  Sodium  chlorite  is  NaClO2. 

Chloric  Tetroxide,  Symbol  C12O4,  is  an  explosive  gas  ob 
tained  by  the  action  of  sulphuric  acid  on  potassium  chlorate. 

Chloric  Pentoxide,  Symbol  C12O6,  has  not  been  as  yet  iso 
lated  ;  but  the  acid  derived  from  it  is  known,  viz.  : 

Chloric  Acid.  Symbol  H  C1O3.  Combining  Weight  84-5. 
Certain  metallic  salts  corresponding  to  this  body  (and  termed 
chlorates)  are  obtained  by  the  action  of  chlorine  in  excess 
upon  the  warm  solution  of  the  metallic  oxide,  thus : 

3  Cl>  +  6  KHO  =  KC103  +*5KC1  +  3  H2O. 

Chlorine,  and  potash,  give  potassium  chlorate,  potassium 
chloride,  and  water. 

The  chlorate  can  be  easily  separated  from  the  more  solu 
ble  chloride  by  crystallization.  Chloric  acid  (hydric  chlorate) 
itself  can  be  prepared  by  decomposing  potassium  chlorate  by 
hydrofluosilicic  acid,  whereby  an  insoluble  potassium  com 
pound  is  precipitated,  and  chloric  acid  remains  in  solution  ; 
or  by  adding  sulphuric  acid  to  barium  chlorate,  insoluble, 
barium  sulphate  being  precipitated,  thus  : 

Ba  2  C1O3  +  H2  So4  =  Ba  SO4  +  2  (H  C1O»). 

Chloric  acid  solution  may  be  concentrated  to  a  syrup,  but 
it  decomposes  on  further  evaporation ;  it  acts  as  a  powerful 
oxidizing  agent,  and  when  dropped  upon  paper  it  produces 
ignition,  parting  with  its  oxygen.  The  chlorates  also  yield 
up  all  their  oxygen  on  heating,  and  the  potassium  salt  is  used 
as  a  most  convenient  source  of  this  gas.  The  composition 
of  chloric  acid  is  ascertained  by  determining  the  weight  of 
oxygen,  which  potassium  chlorate  yields  on  heating  (see  ante, 
p.  12),  together  with  the  amount  of  chlorine  contained  in  the 
residual  potassium  chloride. 


94  Elementary  Chemistry. 

Chloric  Heptoxide,  Symbol  CLOT,  is  unknown  as  yet  in  the 
free  state.     Its  corresponding  acid  is  known,  viz. : 

Perchloric  Acid.  Symbol  HC1O4.  Combining  Weight 
100-5.  When  potassium  chlorate  is  heated,  it  first  fuses  and 
begins  to  give  off  oxygen  :  at  a  certain  point,  however,  the 
whole  mass  solidifies  ;  if  the  decomposition  be  stopped  at  this 
stage  a  new  salt  will  be  found  to  be  contained  in  the  residue,' 
together  with  chloride  and  unaltered  chlorate.  This  is  termed 
Potassium  perchlorate,  and  its  composition  is  KC1O4.  It 
may  be  easily  separated  from  the  chlorate  by  the  action  of 
hydrochloric  acid,  which  decomposes  this  latter,  but  has  no 
action  on  the  perchlorate.  Perchloric  acid,  HC1O4,  can  easi 
ly  be  prepared  from  the  potassium  salt  by  the  action  of  strong 
sulphuric  acid.  If  a  mixture  of  one  part  of  the  dry  perchlo 
rate  and  four  of  sulphuric  acid  be  distilled  in  a  retort,  a  color 
less  fuming  liquid  condenses  in  the  receiver  ;  this  is  per 
chloric  acid,  HC1C>4.  It  has  a  specific  gravity  of  178  at  I5°'5, 
and  does  not  solidify  at-  35°.  Perchloric  acid  is  one  of  the 
most  powerful  oxidizing  agents  known  ;  when  thrown  upon 
wood  or  paper  it  produces  instant  ignition,  and  when  dropped 
on  to  charcoal  it  decomposes  with  a  loud  explosion.  It  com 
bines  with  water  to  form  a  crystalline  hydrate,  HC1O4  +  H2O, 
which  when  further  diluted  with  water  forms  a  thick  oily 
liquid,  boiling  constantly  at  203°,  and  containing  72*3  per 
cent,  of  HC1O4,  and  thus  not  corresponding  to  any  definite 
hydrate.  Perchloric  acid  is  by  far  the  most  stable  of  the  acids 
derived  from  chlorine. 


Compounds  of  Chlorine  and  Nitrogen. 

Chlorine  combines  with  nitrogen,  though  only  indirectly,  to 
form  a  very  remarkable  compound,  the  composition  of  which 
has  not  been  as  yet  determined.  If  chlorine  gas  is  passed  into 
a  solution  of  ammonia,  nitrogen,  as  we  have  seen,  is  liberated  ; 
if  an  excess  of  chlorine  be  employed,  drops  of  an  oily  liquid 
are*  seen  to  form,  which,  on  being  touched,  explode  with  fear* 


Elementary  Chemistry.  95 

ful  violence,  so  that  the  greatest  caution  must  be  used  in 
manipulating  even  traces  of  this  body.  The  explosive  nature 
of  this  compound  arises  from  the  fact  that  its  constituent  ele 
ments  are  very  loosely  combined,  and  separate  with  sudden 
violence. 

Compounds  of  Chlorine  and  Carbon. 

-    Chlorine  and   carbon   unite  to  form   four  different  com 
pounds,  which  will  be  discussed  under  Organic  Chemistry. 




LESSON  XL 
BROMINE.    Symbol  Br.     Combining  Weight  80.    Density  80. 

This  element,  which  closely  resembles  chlorine  in  its  prop 
erties  and  compounds,  was  discovered  by  Balard,  in  1826, 
in  the  salts  obtained  by  the  evaporation  of  sea-water.  It 
does  not  occur  free  in  nature,  and  is,  like  chlorine,  found  com 
bined  with  sodium  and  magnesium  in  the  waters  of  certain 
mineral  springs.  In  order  to  obtain  pure  bromine,  use  is 
made  of  the  fact  that  free  chlorine  liberates  bromine  from  its 
combinations  with  metals,  forming  a  metallic  chloride.  The 
bromine  thus  set  free  may  be  separated  by  shaking  the  liquid 
up  with  ether,  which  dissolves  the  bromine,  forming  a  bright 
red  solution.  On  adding  caustic  potash  to  this  ethereal  solu 
tion,  the  color  at  once  disappears,  the  bromine  becomes  com 
bined,  forming  potassium  bromide,  and  bromate  :  on  evapo 
ration  of  the  ether  these  salts  remain,  and  after  ignition  (to 
decompose  the  bromate),  the  bromine  can  again  be  liberated 
by  the  action  of  sulphuric  acid  and  manganese  dioxide, 
exactly  as  in  the  case  of  chlorine. 

;2SO4  +  MnSO4  +  2H2O. 


Potassium  bromide,   and   sulphuric  acid,  and  manganese 


96  Elementary  Chemistry. 

dioxide,  give  bromine,  potassium  sulphate,  manganese  sul 
phate,  and  water. 

Bromine  is  a  dark,  reddish-black,  heavy  liquid  (the  only 
element  liquid  at  ordinary  temperatures  besides  mercury)  : 
its  specific  gravity  at  4°  is  2-966  ;  it  freezes  at  —  22°  to  a  black 
solid,  and  boils  at  63°.  It  possesses  a  very  strong,  irritating 
smell,  resembling  that  of  chlorine  (^pw^oj  a  stink),  and,  when 
inhaled,  acts  as  a  strong  poison  :  one  part  of  bromine  dissolves 
in  about  30  parts  of  water  at  15° ;  and  this  solution  possesses 
bleaching  powers,  feebler,  however,  in  action  than  those  of 
chlorine.  This  bleaching  action  is  caused  by  the  oxidation  of 
the  coloring  matter,  bromine  combining  with  the  hydrogen  of 
the  water  to  form  an  acid  called  hydrobromic  acid,  correspond 
ing  in  mode  of  formation  and  properties  to  hydrochloric  acid. 
Hydrobromic  Acid,  or  Hydric  Bromide.  Symbol  HBr. 
Combining  Weight  81.  Density  40*5. 

Hydrogen  and  bromine  do  not  unite  together,  even  when 
placed  in  the  sunlight,  but  they  combine  to  form  hydro 
bromic  acid  when  passed  through  a  red-hot  porcelain  tube. 
Hydrobromic  acid  is  prepared  by  the  action  of  acids  (phos 
phoric  acid)  on  the  bromides ;  it  is  a  colorless  gas,  having  a 
strong  acid  reaction,  and  fumes  strongly  in  moist  air :  it  is 
very  soluble  in  water.  When  concentrated,  the  aqueous  acid 
boils  (under  760  mm.  pressure)  at  126°,  and  contains  47-8  per 
cent,  of  HBr.  Two  volumes  of  this  gas  contain  one  of 
bromine  united  with  one  of  hydrogen.  The  aqueous  acid 
neutralizes  bases,  forming  the  bromides  and  water.  The  gas 
liquefies  at  -  73°. 


Compounds  of  Bromine  with  Oxygen. 

These  are  analogous  to  those  of  Chlorine,  although  not 
so  numerous. 

Hypobromous  Oxide,  Br3O,  is  not  known,  but  the  cor 
responding  Hypobromous  Acid,  HBrO,  is  known,  though 


Elementary  Chemistry.  97 

only  in  aqueous  solution.  It  is  obtained  by  the  action  of 
bromine  water  upon  mercuric  oxide  ;  like  hypochlorous  acid, 
it  bleaches  vegetable  coloring  matters  by  oxidation,  hydro- 
bromic  acid  being  formed.  Bromic  Pentoxide,  Br2O5,  has 
not  yet  been  isolated,  but  the  corresponding  Bromic  Acid, 
HBrO3,  can  be  obtained  by  the  action  of  chlorine  upon 
bromine  water,  thus  : 

Br  +  3H2O  +  5C1  =  5HC1  +  HBrO3. 

In  both  its  properties  and  composition  it  corresponds  to 
chloric  acid.  Certain  metallic  bromates  can  be  obtained, 
like  the  corresponding  chlorates,  by  the  action  of  bromine  on 
the  metallic  oxides  in  aqueous  solution.  The  best  method  of 
obtaining  the  bromates  of  the  alkaline  metals  (potassium  and 
sodium)  consists  in  saturating  a  concentrated  solution  of  the 
metallic  carbonate  with  chlorine  until  carbonic  acid  begins  to 
escape,  and  then  adding  bromine  ;  all  the  chlorine  escapes, 
and  solution  of  pure  bromate  remains.  Hence  it  appears 
that  bromine  can  displace  chlorine  from  its  compounds  with 
oxygen,  whilst  chlorine  can  liberate  bromine  from  its  com 
pound  with  hydrogen.  The  bromates  are  decomposed  by 
heat  in  the  same  way  as  the  chlorates. 

Perbromic  Acid,  or  Hydric  Perbromate,  HBrC>4,  has  been 
obtained  by  the  action  of  bromine  upon  perchloric  •  acid, 
HC1O4. 


IODINE.     Symbol  I.     Combining  Weight  127.     Density  127. 

Iodine  likewise  occurs  in  sea-water,  and  is  obtained  from 
kelp,  the  ash  of  certain  seaweeds,  in  which  it  is  found  com 
bined  with  sodium  and  magnesium,  forming  compounds 
called  Iodides.  It  was  discovered  in  1812  by  Courtois. 
Iodine  is  obtained  from  kelp  by  exactly  the  same  process  as 
that  by  which  chlorine  and  bromine  are  obtained  from  chlo 
rides  and  bromides,  viz.  by  heating  with  sulphuric  acid  and 
manganese  dioxide.  Iodine  is  thus  liberated  in  the  form  of  a 


98  Elementary  Chemistry. 

deep  violet-colored  vapor,  which  condenses  to  a  dark  gray 
solid,  with  bright  metallic  lustre.  Iodine  melts  at  115°,  and 
boils  above  200°,  and  has  a  specific  gravity  of  4-95  ;  it  gives 
off  a  perceptible  amount  of  vapor  at  the  ordinary  temperature, 
and  possesses  a  faint,  chlorine-like  smell.  Water  dissolves 
a  very  small  quantity  of  iodine  ;  but,  in  presence  of  a  soluble 
iodide,  it  is  freely  dissolved,  forming  a  deep  red  or  brown 
solution :  it  is  easily  soluble  in  alcohol  and  other  organic 
liquids.  Iodine  does  not  possess  such  active  properties  as 
either  of  the  preceding  elements,  its  solution  does  not  bleach 
organic  coloring  matters,  and  it  is  liberated  from  its  com 
pounds  by  both  bromine  and  chlorine.  Free  iodine  forms  a 
remarkable  compound  with  starch,  of  a  splendid  blue  color, 
and  by  this  means  the  minutest  trace  of  this  substance  can 
be  detected.  To  apply  this  test,  one  drop  of  potassium 
iodide  solution  is  added  to  starch  paste  largely  diluted  with 
water  ;  no  blue  color  is  observed  until  the  iodine  is  set  free 
by  the  addition  of  a  drop  or  two  of  chlorine-water,  when  a 
deep  blue  coloration  is  instantly  perceived.  Iodine  acts  as  a. 
powerful  poison,  but,  given  in  small  quantities,  it  is  much  used 
as  medicine. 

Hydriodic  Acid,  or  Hydric  Iodide.  Symbol  HI.  Combin 
ing  Weight  128.  Density  64.  Iodine  and  Hydrogen  may 
be  ma*de  to  unite  with  each  other  by  heating  them  together  : 
hydriodic  acid  is  liberated  when  dilute  sulphuric  acid  acts  on 
an  iodide.  This  substance  is,  however,  best  prepared  by 
acting  upon  the  phosphoric  iodides  with  water,  thus  : 

PI,  +  3HaO  =  3HI  +  H3  POS. 

Phosphoric  tri-iodide  and  water  produce  hydriodic  acid  and 
phosphorous  acid. 

Hydriodic  acid  is  a  colorless  gas,  possessing  a  strong  acid 
reaction,  and  fuming  strongly  in  the  air :  it  is  very  soluble 
in  water,  yielding  a  solution  which  boils  at  127°,  and  contains 
57  per  cent,  of  HI.  The  gas  liquefies  under  pressure,  and 
solidifies  at  -  55°.  An  analysis  of  this  gas  shows  that  hydri 
odic  acid  (like  hydrochloric)  is  composed  of  one  volume  of 


Elementary  Chsmistry.  99 

hydrogen  and  one  of  iodine,  forming  two  volumes  of  hydriodic 
acid. 

Compounds  of  Iodine  with  Oxygen. 

Iodine,  when  treated  with  caustic  alkaline  solutions,  does 
not  yield  bleaching  liquors  ;  nor  is  there  any  compound  cor 
responding  to  hypochlorous  acid  known  in  the  iodine  series. 
It  forms,  however,  two  important  acids,  iodic  and  per-iodic 
acids,  corresponding  respectively  with  chloric  and  perchloric 
acids ;  the  oxide,  I2O7,  corresponding  with  the  latter,  is  also 
known.  lodic  pentoxide,  IsOs,  is  obtained  as  a  white  crystal 
line  solid  by  heating  iodic  acid,  HIO3,  to  170°. 

Iodic  Acid,  or  Hydric  Iodate.  Symbol  HI O3.  Combining 
Weight  176.  This  acid,  which  corresponds  closely  with 
chloric  acid,  may  be  obtained  by  the  direct  oxidation  of  iodine 
by  nitric  acid,  and  also  by  acting  upon  iodine  water  with 
chlorine,  thus  : 

I  +  3H20  •+  sCl  =  HI03  +  sHCl. 

Iodine,  water,  and  chlorine,  yield  iodic  acid  and  hydro 
chloric  acid. 

The  alkaline  iodates  are  formed  (together  with  the  iodides 
of  the  metals  employed)  like  the  chlorates  and  bromates,  by 
dissolving  iodine  in  the  caustic  alkalies. 

61  +  6HKO  =  KI03  +  5KI  +  sH2O. 

Iodine  and  caustic  potash,  give  potassium  iodate,  potassium 
iodide,  and  water. 

The  whole  of  the  iodine  is  converted  into  iodate  if  chlorine 
gas  be  passed  into  the  solution,  thus  : 

I  +  6KHO  +  50  =  KIOs  +  5KC1  +  3H2O. 

Iodine,  caustic  potash,  and  chlorine,  yield  potassium  iodate, 
potassium  chloride,  and  water. 

Hence  we  see  that  oxygen  combines  with  iodine  to  form  an 
iodate  in  preference  to  forming  a  chlorate  with  chlorine.  The 
iodates  of  the  alkaline  metals  decompose  on  heating  like  the 


IOO  Elementary  Chemistry. 

corresponding  chlorates,  yielding  oxygen  and  an  iodide, 
whereas  the  iodates  of  the  heavy  metals  yield  the  metallic 
oxides,,  iodine,  and  oxygen. 

lodic  Heptoxide,  I2O7,  has  recently  been  prepared. 

Per-iodic  Acid,  HIO4,  or  Hydric  Per-iodate,  can  be  obtained 
from  the  corresponding  perchloric  acid  by  the  addition  of 
iodine. 

FLUORINE.     Symbol  F.     Combining  Weight  19. 

This  element  occurs  combined  with  the  metal  calcium, 
forming  calcium  fluoride  CaF2,  or  fluorspar,  a  mineral  crys 
tallizing  in  cubes  and  found  in  Derbyshire  ;  it  also  exists  in 
large  quantities  in  cryolite  (3  NaF  +  A1F3),  a  mineral  found 
in  Greenland,  whilst  it  has  been  detected  in  minute  quantities 
in  the  teeth,  and  even  in  the  blood  of  animals.  Fluorine  is 
remarkable  as  forming  no  compounds  with  oxygen,  and  as 
being  extremely  difficult  to  prepare  in  a  pure  state.  Many 
unsuccessful  attempts  have  been  made  to  obtain  fluorine,  but 
none  of  the  methods  which  yield  chlorine,  bromine,  or  iodine 
give  any  result.  By  the  action,  however,  of  dry  iodine  upon 
dry  silver  fluoride,  it  appears  that  fluorine  has  been  isolated, 
and  it  is  found  to  be  a  colorless  gas  which  does  not  act  upon 
glass,  and  is  absorbed  by  caustic  potash  with  the  formation 
of  potassium  fluoride  and  hydric  dioxide. 

2  KHO  +  F2  =  2.  KF  +  H202. 

Hydrofluoric  Acid,  or  Hydric  Fluoride.  Symbol  HF. 
Combining  Weight  20.  Density  10. 

This  gas  corresponds  in  composition  to  the  hydrogen  com 
pounds  of  the  three  preceding  elements,  and  may  be  obtained 
in  an  exactly  similar  manner  by  the  action  of  sulphuric  acid 
upon  calcium  fluoride,  thus  : 

H2  SO4  +  CaF2  =  2  HF  +  Ca  SO4. 

Sulphuric  acid,  and  calcium  fluoride,  give  hydrofluoric  acid 
and  calcium  sulphate. 

Hydrofluoric  acid  gas  must  be  prepared  in  a  leaden  or 


Elementary  Chemistry.  IOI 

platinum  vessel  (Fig.  30),  as  glass  is  rapidly  attacked  by  the 
vapor.  The  colorless  gas  thus  obtained  fumes  strongly  in 
the  air ;  if  it  be  passed  into  a  metallic  tube  (Fig.  30)  placed 
in  a  freezing  mixture  of  the  temperature  of -20°,  a  liquid  is 
formed  ;  this  liquid  is  strong  aqueous  hydrofluoric  acid  :  it 
appears  doubtful  whether  the  dry  acid  HF  has  been  obtained 
in  the  liquid  state.  The  strong  acid  acts  very  violently  upon 
the  skin,  producing  painful  wounds  ;  and  the  fumes  of  the  gas 
"are  likewise  dangerous  from  their  corrosive  power.  When 
brought  into  contact  with  water  the  strong  acid  dissolves 


FIG.  30. 

with  a  hissing  noise;  this  aqueous  acid  attains  a  constant 
boiling  point  under  the  ordinary  atmospheric  pressure,  when 
the  liquid  contains  37  per  cent,  of  HF. 

The  most  remarkable  property  of  hydrofluoric  acicf  is  its 
4)ower  of  etching  upon  glass  ;  this  arises  from  the  fact  that 
fluorine  forms,  with  the  silicon  contained  in  the  glass,  a  vola 
tile  compound  called  Silicic  Fluoride  (see  p.  123).  This  etching 
serves  as  a  very  delicate  test  of  the  presence  of  fluorine,  and 
is  eifected  in  a  very  simple  manner  by  covering  a  watch-glass 
with  a  thin  coating  of  wax,  removing  a  portion  by  means  of  a 
sharp  point,  and  then  exposing  the  glass  for  a  short  time  to 
the  vapor  of  hydrofluoric  acid  given  offby  heating  the  materials 
in  a  small  leaden  sauce? ;  on  removing  the  wax  with  a  little 
turpentine,  the  marks  on  the  glass  will  be  distinctly  visible. 
The  solution  of  hydrofluoric  acid  in  water  is  also  used  for  the 
purpose  of  etching  on  glass.  Fluorspar  is  used  in  metal- 
iurgic  operations  as  a  flux,  whence  its  name  (flue,  to  flow). 


IO2  Elementary  Chemistry. 

The  members  of  the  foregoing  group  of  elements  exhibit 
certain  remarkable  relations  among  themselves,  especially  a 
gradation  in  properties.  Thus  chlorine  is  a  gas,  bromine  a 
liquid,  and  iodine  a  solid,  at  ordinary  temperatures  ;  the  spe 
cific  gravity  of  liquid  chlorine  is  1-33,  of  bromine  2-97,  and  of 
iodine  4-95 ;  liquid  chlorine  is  transparent,  bromine  but 
slightly  so,  and  iodine  is  opaque.  The  combining  weight, 
and,  therefore,  the  density  of  bromine,  is  nearly  the  mean  of 

those  of  chlorine  and  iodine,  ^-^— ;    — -  =  81-25  J  an^  in  its 

general  chemical  deportment  bromine  stands  half-way  between 
the  other  two  elements.  The  property  which  distinguishes 
these  substances  from  the  rest  of  the  elements  is  the  power 
of  forming,  with  hydrogen,  compounds  containing  equal 
volumes  of  the  constituent  gases  united  without  condensa 
tion. 


LESSON  XII. 

SULPHUR.    Symbol  S.    Combining  Weight  32.    Density  32. 
Sulphur  occurs  both  free  and  combined  in  nature;  it  is 


FIG.  31. 


found  free  in  certain  volcanic  countries,  especially  in  Sicily' 
and  Iceland,  and  occurs  crystallized  in  yellow  transparent 
crystals  in  the  form  of  rhombic  octahedra  (Fig.  31) ;  it  exists 


Elementary  Chemistry. 


103 


in  combination  with  many  metals,  forming  compounds  termed 
Sulphides,  which  constitute  the  common  ores  from  which  the 
metals  are  usually  obtained.  Thus  PbS,  lead  sulphide,  or 
Galena;  Zn  S,  zinc  sulphide,  or  Blende;  and  Cu  S,  copper 
sulphide,  are  the  substances  from  which  those  metals  are 
generally  procured.  Sulphur  also  is  found  in  nature,  com 
bined  with  metals  and  oxygen,  to  form  a  class  of  salts  called 
Sulphates  ;  of  these,  calcium  sulphate  or  gypsum,  barium  sul- 
"phate  or  heavy  spar,  sodium  sulphate  or  Glauber's  salt,  occur 
in  the  largest  quantity.  Sulphur  likewise  occurs  combined 
with  hydrogen  as  a  gas  called  Hydric  Sulphide,  or  Sulphu 
retted  Hydrogen,  H2S,  in  the  waters  of  certain  springs,  as  at 
Harrogate.  In  order  to  obtain  pure  sulphur,  the  mineral  con 
taining  the  crude  substance  mixed  with  earthy  impurities  is 
heated  in  earthenware  pots  (Fig.  32) ;  the  sulphur  distils  over 


FIG.  32. 

In  the  form  of  vapor,  which  is  condensed  in  similar  pots 
placed  outside  the  furnace.  When  brought  to  this  country, 
the  sulphur  thus  obtained  is  refined  or  purified  by  subjecting 
it  to  a  second  distillation.  If  the  vapor  of  sulphur  is  quickly 


IO4  Elementary  Chemistry. 

cooled  below  its  melting-point,  it  solidifies  in  the  form  of  a 
fine  crystalline  powder  called  Flowers  of  Sulphur,  exactly  as 
aqueous  vapor,  when  cooled  down  below  the  freezing  point  of 
water,  deposits  as  snow.  When  sulphur  is  gently  heated  it 
melts,  and  may  be  cast  into  sticks,  and  is  then  known  as 
brimstone  or  roll  sulphur. 

Sulphur  exists  in  three  modifications  :  the  first  is  that  in 
which  sulphur  crystallizes  in  nature,  and  the  other  two  are 
obtained  by  melting  sulphur.  If  melted  sulphur  be  allowed  to 
cool  slowly,  it  crystallizes  in  long,  transparent,  needle-shaped, 
prismatic  crystals,  which  are  quite  different  in  form  from  the 
natural  crystals  of  sulphur,  and  have  the  specific  gravity  of 
I '98;  whereas  the  specific  gravity  of  the  crystals  of  na 
tive  sulphur  is  2*07.  These  transparent  crystals  become 
opaque  after  exposure  to  the  air  for  a  few  days,  owing  to  each 
crystal  splitting  up  into  several  crystals  of  the  natural,  octahe 
dral,  or  permanent  form.  The  third  allotropic  modification 
of  sulphur  is  obtained  by  pouring  melted  sulphur  heated  to 
230°  into  cold  water ;  the  sulphur  thus  forms  a  soft  tenacious 
mass  resembling  caoutchouc,  and  has  a  specific  gravity  of 
1*96.  This  form  of  sulphur  is,  however,  not  permanent ;  in  a 
few  hours,  at  the  temperature  of  the  air,  the  mass  assumes  the 
ordinary  brittle  form  of  the  element,  while,  if  heated  to  100°, 
it  instantly  changes  to  the  brittle  form,  and  thereby  evolves 
so  much  heat  as  to  raise  its  temperature  up  to  m°.  These 
peculiar  modifications  become  apparent  when  sulphur  is 
heated  ;  thus,  sulphur  melts,  to  begin  with,  at  115°,  and  forms 
an  amber-colored  mobile  liquid  ;  as  the  temperature  rises,  the 
liquid  becomes  dark-colored,  and  attains  the  consistency  of 
thick  treacle,  so  that  at  about  230°  it  can  scarcely  be  poured 
out  of  the  vessel :  heated  above  250°  it  again  becomes  fluid, 
and  remains  as  a  dark  reddish-black-colored  thin  liquid,  until 
the  temperature  rises  to  490°,  when  it  begins  to  boil  and  gives 
off  a  red-colored  vapor. 

Sulphur  is  an  inflammable  substance,  and  when  heated  in 
the  air  or  in  oxygen,  burns  with  a  bluish  flame,  combining 
with  the  oxygen  to  form  sulphuric  dioxide  (often  called  sul- 


Elementary  Chemistry.  105 

phurous  acid),  SO2,  which  is  given  off  as  a  gas  possessing  the 
peculiar  and  well-known  suffocating  smell  which  is  evolved 
when  a  common  lucifer  match  is  burnt.  Sulphur  is  insoluble 
in  water  and  most  organic  liquids,  but  both  the  natural  octahe 
dral  variety,  and  the  other  crystalline  (or  prismatic)  variety, 
dissolve  freely  in  carbonic  di-sulphide,  CS2,  whilst  the  tena 
cious  form  of  sulphur  is  insoluble  in  this  liquid.  When  de 
posited  from  solution  in  carbonic  di-sulphide,  sulphur  crystal 
lizes  in  the  ordinary  natural  or  octahedral  form. 


Compounds  of  Sulphur  and  Oxygen. 

Two  compounds  of  sulphur  and  oxygen  are  known  in  the 
free  state,  viz.  the  di-oxide,  SO3,  and  the  tri'oxide,  SO3 :  whilst 
acids  corresponding  to  several  others  are  known,  as  are  also 
several  extensive  series  of  well  defined  metallic  salts  thence 
derived.  The  following  table  shows  the  composition  of  seven 
sulphur  oxacids  ;  the  first  three  on  the  list  are  important  com 
pounds,  the  remaining  bodies  are  but  little  known,  and  do  not 
as  yet  serve  any  purpose  in  the  arts  or  manufactures.  These 
compounds  exhibit  in  a  striking  manner  the  law  of  multiple 
combining  proportions  enumerated  by  Dalton.  (See  ante, 
p.  50.) 

,  Hydric  Sulphite  or  Sulphurous  Acid H-^S  O3 

Hydric  Sulphate  or  Sulphuric  Acid HaS  O4 

Hydric  Hyposulphite  or  Hyposulphurous  Acid 
Hydric  Dithionate  or  Dithionic  Acid 
Hydric  Trithionate  or  Trithionic  Acid 
Hydric  Tetrathionate  or  Tetrathionic  Acid 
Hydric  Pentathionate  or  Pentathionic  Acid 

Sulphuric  Dioxide  or  Sulphurous  Add.  Symbol  SO2. 
Combining  Weight  64.  Density  32. 

This  gas  is  obtained  when  sulphur  is  burnt,  and  it  is  given 
off  in  large  quantities  from  volcanic  craters  ;  it  may  be  pre-» 
pared  more  conveniently  on  the  small  scale  by  removing  the 
elements  of  water,  and  one  additional  atom  of  oxygen  from 

5* 


io6 


Elementary  Chemistry. 


sulphuric  acid  by  heating  along  with  it  the  metals  copper  or 
mercury,  thus  : 

Cu-f  2H2  SO4  =  SOa  +  Cu  SO4  +  2H2O. 

Copper,  and  sulphuric  acid,  yield  sulphuric  dioxide,  copper 
sulphate,  and  water. 

The  gas  thus  given  off  may  be  washed  to  purify  it  and  then 
collected  over  mercury  or  by  displacement.  It  is  a  colorless 
gas,  possessing  a  suffocating  smell  of  burning  sulphur  ;  it  is 
2-247  times  heavier  than  air,  and  may  be  condensed  to  a  col 
orless  liquid  by  cooling  down  to  -  10°  under  the  ordinary 
atmospheric  pressure  ;  when  cooled  below  -76°  the  liquid 
freezes  to  a  transparent  solid.  The  arrangement  for  liquefy 
ing  the  gas  is  seen  in  Fig.  33  :  it  consists  of  the  usual  evolu- 


FIG.  33- 

tion  flask  and  washing  bottle,  which  is  connected  with  a  spiral 
glass  tube  surrounded  by  a  freezing  mixture  of  salt  and 
pounded  ice.  The  gas  condenses  in  this  tube  and  falls  down 
•into  the  small  flask  placed  below,  which  is  also  placed  in  a 
freezing  mixture.  When  a  sufficient  quantity  of  the  liquid  has 
been  collected,  the  neck  of  the  flask  can  be  sealed  up  by  the 


Elementary  Chemistry.  107 

blowpipe  at  the  narrow  part,  and  the  liquefied  sulphuric 
dioxide  preserved.  This  liquid  evaporates  very  quickly  when 
brought  into  the  air,  and  the  heat  which  thus  becomes  latent 
is  so  considerable,  that  the  temperature  may  in  this  way  be 
reduced  to  -60° ;  this  is  easily  shown  by  pouring  some  of  the 
liquid  upon  the  bulb  of  an  alcohol  thermometer  which  has 
been  wrapped  in  cotton  wool. 

Sulphuric  dioxide,  like  all  other  gases  which  are  easily 
"condensed,  exhibits  considerable  deviation  from  Boyle's  law 
of  pressures,  occupying  for  equal  increments  of  pressure  less 
space  than  air  under  the  same  conditions  ;  this  difference 
becoming  larger  the  lower  the  temperature.  The  volume  of 
this  gas  formed  by  the  combustion  of  sulphur  is  found  to  be 
exactly  the  same  as  that  of  the  oxygen  employed.  Hence, 
as  the  density  of  sulphuric  dioxide  is  32,  it  contains  equal 
weights  of  its  constituent  elements,  I  volume  of  sulphur 
uniting  with  2  volumes  of  oxygen  to  give  2  volumes  of  the  di 
oxide. 

Sulphuric  dioxide  is  very  soluble  in  water,  I  volume  of 
water  at  10°  dissolving  51  -38  volumes,  and  at  20°  36*22  vol 
umes  of  this  gas.  The  solution  of  the  gas  in  water  consists 
(like  that  of  carbonic  dioxide,  p.  71)  of  di-hydric  sulphite  or 
true  sulphurous  acid,  H2  SO3 :  but  this  substance  is  decom 
posed  on  boiling  the  liquid,  water  and  sulphurous  dioxide 
being  reproduced,  this  latter  escaping  as  a  gas.  If  the  solu 
tion  of  this  gas  in  water  be  cooled  below  5°,  a  crystalline 
hydrate  of  sulphurous  acid  separates  out,  having  the  composi 
tion  H2  SO3  -f  14  H2O. 

Sulphurous  acid  is  really  the  hydrogen  salt  in  a  series  of 
compounds  called  sulphites  ;  these  compounds,  however,  are 
easily  decomposed  by  the  stronger  acids,  sulphurous  dioxide 
being  liberated  as  a  gas.  This  substance  is  largely  used  as  a 
bleaching  agent,  especially  for  silk  and  woollen  goods  which 
cannot  be  bleached  by  chlorine  ;  it  is  also  employed  as  an 
antichlor  for  the  purpose  of  getting  rid  of  the  excess  of 
chlorine  present  in  the  bleached  rags  from  which  paper  is 
made.  The  great  value  of  sulphurous  dioxide  in  the  arts  is  in 


io8  Elementary  Chemistry. 

the  manufacture  of  sulphuric  acid  or  oil  of  vitriol,  and  for  this 
purpose  enormous  quantities  of  the  dioxide  are  used. 

Sulphurous  acid,  H2  SO3,  like  carbonic  acid,  H2  CO3,  is  a 
dibasic  acid,  that  is,  it  contains  two  atoms  of  hydrogen,  both 
of  them  being  capable  of  being  replaced  by  metals :  thus  two 
classes  of  salts  are  derived;  the  so-called  acid  salts,  where 
only  one  atom  of  hydrogen  has  been  replaced,  and  the  neutral 
salts,  where  both  atoms  have  been  replaced  by  a  metal.  Thus 
— Hydric  Potassium  Sulphite,  HK  SO3,  is  an  acid  salt,  and 
Dipotassium  Sulphite,  K2  SO3,  is  a  neutral  salt.  Similarly, 
we  have  Hydric  Potassium  Carbonate,  HK  CO3,  and  Dipo 
tassium  Carbonate,  K2  CO3. 

In  its  bleaching  action,  sulphurous  dioxide  acts  in  a  manner 
exactly  opposite  to  that  in  which  chlorine  acts,  inasmuch  as 
it  unites  with  the  oxygen  of  the  water  or  coloring  matter 
present,  forming  sulphuric  acid  and  liberating  the  hydrogen  ; 
so  that  sulphurous  acid  bleaches  by  acting  as  a  reducing  or 
deoxidizing  agent,  whereas  chlorine  bleaches  by  oxidation : 
similarly,  its  action  as  an  antichlor  depends  on  the  formation 
of  sulphuric  and  hydrochloric  acids,  thus  : 

=  H2  SO4  +  2HC1. 


LESSON  XIII. 

Sulphuric  Trioxide,  or  Sulphuric  Anhydride.  Symbol 
SO3.  Combining  Weight  80.  Density  40. 

Sulphuric  dioxide  does  not,  under  ordinary  circumstances, 
combine  directly  with  oxygen  to  form  SO3,  but  if  these  two 
dry  gases  be  passed  together  over  heated  and  finely  divided 
metallic  platinum,  union  takes  place,  and  dense  white  fumes 
of  the  sulphuric  trioxide  are  evolved,  condensing  to  white 
silky  needles.  These  crystals  melt  at  29°  and  boil  at  46°, 
yielding  a  colorless  vapor,  which  when  passed  through  a  red- 


Elementary  Chemistry.  109 

hot  tube  is  decomposed  into  two  volumes  of  sulphuric  dioxide 
and  one  volume  of  oxygen.  Sulphuric  trioxide  does  not 
redden  litmus  paper,  and  maybe  moulded  by  the  fingers  with 
out  charring  the  skin  :  when  brought  into  contact  with  water, 
the  two  substances  combine  with  great  force,  forming  sul 
phuric  acid,  H2SO4,  hissing  as  a  red-hot  iron  would  do.  The 
combination  thus  formed  cannot  be  separated  again  into  sul 
phuric  trioxide  and  water  by  boiling.  The  trioxide  may  like- 
"y.'ise  be  prepared  by  distilling  Nordhausen  fuming  sulphuric 
acid  (see  below). 

Sulphuric  Add,  or  Di-hydric  Sulphate.  Combining 
Weight  98. 

This  substance  is  the  most  important  and  useful  acid 
known,  as  by  its  means  nearly  all  the  other  acids  are  prepared, 
and  also  because  it  is  very  largely  used  in  the  arts  and  manu 
factures,  for  a  great  variety  of  purposes.  So  valuable  are  the 
applications  of  this  acid,  that  the  quantity  now  manufactured 
in  the  South  Lancashire  district  alone  exceeds  3,000  tons  per 
week.  Indeed,  it  has  been  truly  said,  that  the  commercial 
prosperity  of  a  country  may  be  judged  of  with  great  accura 
cy  by  the  amount  of  sulphuric  acid  which  it  consumes. 

Sulphuric  acid  was  first  prepared  by  distilling  a  compound 
of  iron,  oxygen,  sulphur  and  water,  called  ferrous  sulphate  or 
green  vitriol.  The  acid  thus  obtained  is  known  as  fuming  or 
Nordhausen  acid,  and  consists  of  a  mixture  of  dihydric  sul 
phate  and  sulphuric  trioxide,  H2SO4  +  SO3.  This  plan  of 
preparation  has,  however,  long  been  superseded  by  the  follow 
ing  more  convenient  method,  which  depends  upon  the  fact, 
that  although  sulphuric  dioxide  does  not  combine  with  free 
oxygen  and  water  to  form  sulphuric  acid,  it  is  capable  of 
taking  up  the  oxygen  when  the  latter  is  united  with  nitrogen 
in  the  form  of  nitric  trioxide,  N2O3,  thus  : 

SO2  +  H2O  +  NaO3  =  H2SO4  +  N,O9. 

Sulphuric  dioxide,  water,  and  nitric  trioxide,  yield  sul 
phuric  acid  and  nitric  oxide. 


no 


Elementary  Chemistry. 


The  nitric  oxide  formed  in  this  decomposition  takes  up  an 
other  atom  of  oxygen  from  the  air,  becoming  N2O3,  and  this 
is  again  able  to  convert  a  second  molecule  of  SO.2  with  H^O 
into  H2SO4,*  being  a  second  time  reduced  to  N2O2,  and 
ready  again  to  take  up  another  atom  of  oxygen  from  the  air. 
Hence  it  is  clear  that  the  N2O2  acts  simply  as  a  carrier  of 
oxygen  between  the  air  and  the  SO2  ;  an  indefinitely  small 
quantity  of  this  nitric  trioxide  being,  therefore,  theoretically 


FIG.  34- 

able  to  convert  an  indefinitely  large  quantity  of  sulphurous 
dioxide,  water,  and  oxygen  into  sulphuric  acid.f 

This  process  is  carried  on,  on  the  large  scale,  in  chambers 
made  of  sheets  of  lead  (often  of  a  capacity  of  50,000  or  100,000 

*  A  molecule  is  a  group  of  atoms  forming  the  smallest  portion  of  a  chemical 
substance,  either  simple  or  compound,  that  can  be  isolated,  or  that  can  exist  alone  ; 
it  is  the  smallest  amount  of  substance  that  can  enter  into  any  reaction  or  be  gen 
erated  by  it ;  *\\.atom  being  the  smallest  portion  of  an  element  that  can  exist  in  a 
compound  body  as  a  mass  indivisible  by  chemical  forces  ;  thus  the  molecule  of 
water  H-2  O  contains  2  atoms  of  hydrogen. 

t  There  is  some  doubt  respecting  the  actual  decomposition  occurring  in  the 
leaden  chamber,  and  the  above  must  be  taken  only  as  a  general  explanation  of 
what  goes  on.  If  the  supply  of  steam  be  insufficient,  a  solid  compound  of  nitric 
tetroxide,  sulphuric  dioxide,  and  water  is  formed,  which  is  decomposed,  on  addi 
tion  of  water,  into  sulphuric  acid  and  nitric  oxide.  This  substance,  which  has  been 
called  the  crystals  of  the  leaden  ctiamber,  is  supposed  by  some  to  play  an  important 
part  in  the  formation  of  sulphuric  acid. 


Elementary  Chemistry.  ill 

cubic  feet),  into  which  the  above-mentioned  materials  are 
brought.  Fig.  34  exhibits  the  construction  of  such  a  sul 
phuric  acid  chamber.  The  sulphuric  dioxide  is  procured 
either  by  burning  sulphur  in  a  current  of  air,  or  by  roasting  a 
mineral  called  iron  pyrites  (a  compound  of  sulphur  and  iron, 
FeS2)  in  a  suitable  furnace,  AA,  Fig.  34.  The  sulphur  of  the 
pyrites  burns  away,  and  the  gaseous  product  is  led,  together 
with  atmospheric  air,  into  the  chamber,  whilst  ferric  oxide, 
Fe-jOs,  remains  behind  in  the  furnace.  A  small  stove  (B), 
containing  nitre,  is  placed  in  the  hinder  part  of  the  furnace, 
where  this  salt  is  decomposed  by  the  action  of  the  sulphuric 
dioxide,  an  alkaline  sulphate  being  formed  whilst  nitrous 
fumes  pass  with  the  other  gases  into  the  chamber.  Jets  of 
steam  are  also  blown  into  the  chamber  from  a  boiler  (C)  at 
various  points,  and  a  thorough  draught  is  maintained  by  con 
necting  the  end  of  the  chamber  with  a  high  chimney.  The 
sulphuric  acid,  as  it  forms,  falls  on  to  the  floor  of  the  chamber, 
and  when  the  process  is  working  properly,  it  is  continually 
drawn  off,  attaining  a  specific  gravity  of  about  r6o,  whilst  the 
waste  gases  passing  out  of  the  chamber  should  contain 
nothing  but  nitrogen  and  small  quantities  of  nitric  oxide.  In 
order  to  obtain  from  this  weak  chamber-acid  the  pure  dihy- 
dric  sulphate,  H2SO4,  the  excess  of  water  must  be  removed 
by  evaporation  ;  this  is  conducted,  on  the  large  scale,  first, 
by  heating  the  chamber-acid  in  open  leaden  pans  until  the 
specific  gravity  rises  to  172,  when  the  acid  is  known  as  the 
brown  oil  of  vitriol  of  commerce,  and  then  further  concen 
trated  in  vessels  of  glass,  or  of  platinum  (as  lead  is  attacked 
by  the  strong  acid),  until  its  maximum  strength  and  specific 
gravity  is  attained.  The  dihydric  sulphate  thus  obtained  is  a 
thick  oily  liquid,  boiling  at  about  338°,*  and  freezing  at  io°'8  ; 
its  specific  gravity  at  oc  is  1-854.  It  combines  with  water 
with  great  force,  absorbing  moisture  rapidly  from  the  air  ; 

*  When  boiled,  dihydric  sulphate  undergoes  a  slight  decomposition,  sulphuric 
trioxide  being  evolved,  and  an  acid  remaining  behind  which  contains  only  gS'$ 
of  HiSO4,  and  which  at  338°  C.  may  be  boiled  down  without  further  decompo 
sition. 


112  Elementary  Chemistry. 

hence  it  is  used  in  the  laboratory  as  a  drying  agent.  Great 
heat  is  evolved  when  this  acid  is  mixed  with  water,  and  care 
must  be  taken  to  bring  these  two  liquids  together  gradually, 
otherwise  an  explosive  combination  may  ensue.  Many  or 
ganic  bodies,  such  as  woody  fibre  and  sugar,  are  completely 
decomposed  and  charred  by  strong  sulphuric  acid,  whilst 
others,  such  as  alcohol,  oxalic  and  formic  acid,  are  split  up 
into  other  compounds  by  the  withdrawal  of  the  elements  of 
water  by  this  acid. 

One  molecule  of  dihydric  sulphate  unites  with  one  of  water 
to  form  a  compound,  H2SO4,  4-  H2O,  which  can  be  obtained 
pure  by  cooling  a  mixture  of  acid  and  water,  having  a  specific 
gravity  of  178  down  to  7°C,  at  which  temperature  rhombic 
crystals  of  the  hydrated  acid  are  formed.  The  sulphuric  acid 
of  commerce  frequently  contains  large  quantities  of  impurities, 
especially  lead  sulphate,  from  the  chamber,  and  frequently 
arsenic  from  the  pyrites,  and  nitric  acid,  as  well  as  the  lower 
oxides  of  nitrogen.  In  order  to  free  the  acid  from  these 
impurities,  it  must  be  distilled  and  subjected  to  other  treat 
ment,  for  a  description  of  which  the  reader  is  referred  to  the 
larger  treatises.  At  high  temperatures  sulphuric  acid  decom 
poses  into  sulphuric  dioxide,  SO2,  oxygen,  O,  and  water, 
H2O  ;  thus,  if  a  current  of  the  acid  be  allowed  to  flow  on  to 
red-hot  bricks,  and  the  gases  resulting  from  the  decomposition 
passed  through  water,  the  sulphuric  dioxide  will  be  completely 
absorbed,  and  a  supply  of  pure  oxygen  obtained.  Dihydric 
sulphate  is,  as  its  name  implies,  a  dibasic  acid,  i.e.  it  contains 
two  atoms  of  hydrogen,  either  or  both  of  which  can  be  replaced 
by  an  equivalent  quantity  of  a  metal.  As  with  sulphurous 
acid,  in  the  case  of  the  alkaline  metals,  we  have  two  salts, 
thus — KHSO4  and  K2SO4,  potassium  being  mon-atomic j  that 
is,  one  atom  of  potassium  is  capable  of  replacing  one  of 
hydrogen.  As,  however,  most  of  the  other  metals  are  di-atomic 
— i.e.  one  atom  of  metal  is  capable  of  replacing  two  atoms  of 
hydrogen — we  have  only  one  sulphate  of  these  metals  ;  thus 
barium  sulphate  is  Ba  SO4,  where  Ba  =  H2 :  so  copper  sul 
phate  is  CuSO4,  where  Cu  =  H2.  Barium  and  lead  sulphates 


Elementary  Chemistry.  113 

are  insoluble  in  water ;  hence  soluble  salts  of  these  metals 
are  used  as  tests  of  the  presence  of  a  sulphate  ;  calcium, 
strontium,  and  potassium  sulphates  are  but  slightly  soluble  in 
water,  while  the  other  sulphates  are  easily  soluble. 

Some  sulphates  crystallize  as  anhydrous  salts,  such  as 
K2SO4,  dipotassium  sulphate  ;  Ba  SO4,  barium  sulphate  ;  and 
Ag2SO4,  silver  sulphate  ;  while  others  require  water  to  retain 
their  crystalline  form,  and  this  water  is  termed  water  of  crys 
tallization.  The  crystals  of  iron  sulphate,  or  green  vitriol, 
and  of  zinc  sulphate,  or  white  vitriol,  contain  seven  molecules 
of  water  in  the  solid  form ;  whilst  copper  sulphate,  or  blue 
vitriol,  requires  but  five  molecules  to  preserve  its  crystalline 
form.  Thus — 

7    crj4  T     iVo  anc^  ^"u  ^^4   "^  ^  H2O 

Hyposulphurous  Acid,  or  Hydric  Hyposulphite,  is  not 
known  in  the  free  state.  The  formula  of  a  metallic  hypo 
sulphite,  such  as  that  of  sodium,  is  Na2  S2  Os  ;  this  also  con 
tains  five  molecules  of  water  of  crystallization  ;  it  is  largely 
used  in  photography  for  the  purpose  of  fixing  the  image,  the 
salt  possessing  the  property  of  dissolving  the  silver  salts 
which  have  been  unacted  on  by  the  light.  This  useful  salt  is 
prepared  by  passing  a  current  of  sulphuric  dioxide  into  a 
solution  of  sodium  sulphide,  and  purifying  by  crystallization 
the  sodium  hyposulphite  obtained. 

Sulphuric  trioxide  combines  directly  with  hydrochloric  acid 
to  form  a  compound,  which  is  interesting  in  a  theoretical  point 
of  view;  viz.  chlor-hydrosulphuric  acid,  HC1SO3.  Sulphuric 
dioxide  unites  with  chlorine  to  form  sulphuryl  chloride,  C12 
SO2.  The  first  acid  is  really  sulphurous  acid,  with  one  atom 
of  hydrogen  replaced  by  chlorine. 

*  Compounds  of  Sulphur  and  Hydrogen. 

Two  of  these  are  known,  viz.  dihydric  sulphide,  H2S,  and 
hydric  persulphide,  HiSs. 


114  Elementary  Chemistry. 

Dihydric  Sulphide,  or  Sulphuretted  Hydrogen.  Symbol 
H2S.  Combining  Weight  34.  Density  17. 

This  gas  is  best  prepared  by  the  action  of  dilute  sulphuric 
acid  upon  iron  sulphide,  FeS,  iron  sulphate  being  also  formed 
thus — 

FeS  +  HaSO4  =  FeSO4  +  HaS, 

where  two  atoms  of  hydrogen  change  place  with  one  of  dia 
tomic  iron.  Fig.  35  represents  a  convenient  form  of  apparatus 
for  the  production  and  purification  of  this  gas.  It  may  be 
collected  over  warm  water,  and  is  a  colorless  gas,  possessing 
the  peculiar  odor  of  rotten  eggs  ;  it  burns  on  application  of  a 
light  with  a  bluish  flame,  forming  water  and  sulphuric  dioxide. 
When  inhaled,  it  acts  as  a  poison  on  the  animal  economy, 
even  if  diluted  with  large  quantities  of  air.  Sulphuretted 
hydrogen  gas  dissolves  in  water  to  a  considerable  extent, 


FIG.  35- 

imparting  its  peculiar  smell  and  a  slightly  acid  reaction  to 
the  water.  One  volume  of  water  at  o°  dissolves  4*37  volumes 
of  the  gas,  whilst  at  15°  3-23  volumes  are  soluble.  Exposed 
to  a  temperature  of  -74°,  this  gas  condenses  to  a  colorless, 
mobile  liquid,  which,  when  further  cooled  to  -85°,  freezes  to 
a  transparent,  ice-like  solid.  Under  a  pressure  of  about 
seventeen  atmospheres,  this  gas  liquifies  at  the  ordinary 
temperature  of  the  air.  Sulphuretted  hydrogen  occurs  free 
in  nature  in  volcanic  gases,  as  well  as  in  the  water  of  certain 


Elementary  Chemistry.  11$ 

springs  ;  thus  Harrogate  waters  owe  their  peculiar  odor  and 
medicinal  power  to  the  presence  of  this  gas.  It  is  likewise 
generated  by  the  putrefaction  of  animal  matters,  such  as  albu 
men,  or  the  white  of  eggs,  which  contains  sulphur ;  also  by 
the  deoxidation  of  sulphates  in  presence  of  decaying  organic 
matter. 

The  composition  of  sulphuretted  hydrogen  may  be  ascer 
tained  either  by  heating  a  small  piece  of  metallic  tin  in  a 
known  volume  of  the  gas,  when  tin  sulphide  will  be  formed, 
and  hydrogen  liberated ;  or  by  decomposing  the  gas  by 
means  of  a  red-hot  platinum  wire,  when  the  whole  of  the  sul 
phur  is  deposited,  and  hydrogen  set  free.  In  both  cases,  the 
volume  of  hydrogen  obtained  is  found  to  be  equal  to  that  of 
the  gas  employed  ;  and  hence  2  volumes  of  sulphuretted 
hydrogen,  weighing  34,  consists  of  2  volumes  of  hydrogen, 
weighing  2,  and  I  volume  of  sulphur  vapor,  weighing  32. 

Sulphuretted  hydrogen  is  an  invaluable  re-agent  in  the 
laboratory,  as  by  its  means  we  are  enabled  to  separate  the 
metals  into  groups.  If  we  pass  a  current  of  this  gas  through 
a  solution  of  a  copper  salt,  to  which  a  small  quantity  of  acid 
has  been  added,  we  obtain  an  immediate  precipitate  of  copper 
sulphide  ;  if  we  do  the  same  with  a  solution  of  an  iron  salt, 
we  get  no  such  precipitate,  because  iron  sulphide  is  soluble 
in  an  acid  ;  but  on  the  addition  of  an  alkali,  iron  sulphide  is 
at  once  precipitated.  We  may  thus  divide  the  metals  into 
groups  ;  first,  those  which,  like  copper,  are  precipitated  by 
sulphuretted  hydrogen 'from  an  acid  solution,  or  the  copper 
group;  second,  those  which  are  not  precipitated  by  sulphu 
retted  hydrogen  in  an  acid  solution,  but  which  are  so  precipi 
tated  in  an  alkaline  one,  or  the  iron  group  j  and  third,  those 
which  are  in  no  case  precipitated  by  this  re-agent,  as  their 
sulphides  are  soluble  either  in  water,  acids,  or  alkalies  :  to 
this  group  belong  the  metals  of  the  alkalies  and  alkaline 
earths. 

Hydric  Persulphide,  or  Dihydric  Bisulphide,  H2S2.  This 
substance  is  obtained  by  pouring  a  solution  of  calcium  disul- 
phide  into  hydrochloric  acid  ;  an  oily  liquid  falls  to  the  bottom 


Ii6  Elementary  Chemistry. 

of  the  vessel,  which  is  the  body  in  question.  Hydric  disul- 
phide  closely  resembles  hydric  dioxide  in  many  of  its  proper 
ties  ;  it  bleaches,  and  readily  decomposes  into  sulphur  and 
sulphuretted  hydrogen.  Owing  to  the  solubility  of  sulphur 
in  this  body,  and  the  difficulty  of  purifying  it,  its  composition 
is  not  accurately  ascertained. 

Carbonic  Disulphide.  Symbol  CS2.  Combining  Weight 
76.  Density  38. 

If  the  vapor  of  sulphur  be  passed  over  red-hot  charcoal, 
a  volatile  compound,  CS2,  is  formed,  which  may  be  con 
densed  to  a  heavy,  colorless  liquid,  possessing  a  peculiarly 
disagreeable  smell,  boiling  at  43°'3,  and  having  a  specific 
gravity  of  1-272.  Carbonic  disulphide  is  very  inflammable, 
its  vapor  igniting  at  149°  when  mixed  with  air,  forming  car 
bonic  dioxide,  and  sulphuric  dioxide  (sulphurous  acid),  SO*. 
It  is  insoluble  in  water,  but  acts  as  a  solvent  upon  gums, 
caoutchouc,  sulphur,  and  phosphorus  ;  its  vapor  is,  however, 
very  poisonous,  and  it  must  be  employed  with  caution. 

A  remarkable  analogy  is  presented  by  the  foregoing  sulphur 
compounds  and  the  corresponding  bodies  in  the  oxygen 
series  :  thus  water,  H2O,  and  sulphuretted  hydrogen,  H2S  ; 
hydric  dioxide,  H2O2,  and  hydric  disulphide,  H2S2  ;  carbonic 
dioxide,  CO2,  and  carbonic  disulphide,  CS2,  possess  not  only 
an  analogous  composition,  but  similar  chemical  properties, 
whilst  similar  relations  are  seen  in  many  of  the  compounds  of 
these  bodies. 

Chlorine  and  Sulphur  unite  directly  to  form  two  com 
pounds,  S2C12  and  SC12  ;  they  are  formed  by  leading  a  cur 
rent  of  chlorine  gas  over  melted  sulphur,  and  are  volatile 
liquids,  the  first  boiling  at  138°,  and  the  second  at  64°. 


Elementary  Chemistry.'       H  /^  117 

*     M*    \r 
jN   /   I "  ; 
LESSON  XIV.  s  /  T  \ 

•  w 

SELENIUM.*      Symbol    Se.     Combining    weight  *7&pj\'  i 
Density  79-5. 

Selenium  is  an  element  which  closely  resembles  sulphur  in 
its  properties,  but  it  occurs  in  very  small  quantities  ;  it  was 
discovered  by  Berzelius,  who  found  it  accompanying  sulphur 
in  certain  varieties  of  Swedish  pyrites.  Selenium  also  occurs 
free  in  nature,  and  is  found  in  combination  with  metals  in 
certain  rare  minerals.  Like  sulphur,  it  is  capable  of  existing 
in  various  allotropic  modifications,  one  of  which  is  crystal 
line,  the  other  vitreous  ;  the  crystalline  form  is  obtained  when 
selenium  is  deposited  from  solution  in  carbonic  disulphide  ; 
the  vitreous  modification  results  from  the  cooling  of  melted 
selenium.  The  specific  gravity  of  the  former  variety  is  4-5  ; 
that  of  the  latter.  47.  Crystalline  selenium  melts  at  217°,  . 
and  boils  at  a  temperature  below  a  red  heat,  giving  off  a  deep 
yellow  vapor  ;  vitreous  selenium  softens  at  a  temperature  a 
little  above  the  boiling  point  of  water,  and  remains  in  a  plas 
tic  condition  for  some  time.  In  a  finely  divided  state,  and 
when  seen  by  transmitted  light,  selenium  has  a  red  color.  It 
burns  in  the  air  with  a  bright  blue  flame,  which,  when  ex 
amined  by  means  of  the  spectroscope  (^.  222),  exhibits  a  series 
of  magnificent  and  characteristic  bands.  The  smell  of  burn 
ing  selenium  is  very  peculiar,  resembling  that  of  rotten  cab 
bages,  and  is  due  to  the  formation  of  an  oxide,  the  composi 
tion  and  properties  of  which  are,  however,  as  yet  unknown. 
Selenium  forms  two  well-defined  oxides,  selenic  dioxide,  SeO2, 
and  selenic  trioxide,  SeO3  ;  this  latter,  however,  has  not  as 
yet  been  isolated,  but  the  acid  and  salts  corresponding  with 
it,  and  those  corresponding  with  the  dioxide,  are  well  known, 
and  correspond  exactly  with  the  analogous  sulphites  and  sul 
phates  :  they  are  hence  called  selenites  and  selenates. 

Selenic    Dioxide.       Symbol    SeO2.      Combining    Weight 

*  From  i^£Xii?J"7,  the  moon. 


Ii8  Elementary  Chemistry. 

1  1  1*5.  This  compound  is  formed  when  selenium  is  burnt  in 
the  air,  or  in  pure  oxygen.  It  may  be  prepared,  too,  by 
oxidizing  selenium  in  nitric  acid  or  aqua  regia.  Selenic 
dioxide  is  a  white  crystalline  mass,  capable  of  dissolving  in 
water,  and  thus  forming  selenious  acid,  H2  S£)3.  From  this 
solution  selenium  is  at  once  deposited  on  addition  of  sulphu 
rous  acid,  sulphuric  acid  being  formed,  thus  : 


H2Se08  +  2SOa  +  HaO  =  2(H2  SO4)  +  Se. 

The  metallic  selenites  correspond  closely  with  the  sul 
phites. 

Selenic  Acid,  or  Di-hydric  Selenate.     Symbol  H2SeC>4  . 

This  is  best  prepared  by  fusing  a  selenite  with  nitre  ;  on 
addition  of  a  lead  salt  to  the  solution  of  the  mass  thus  ob 
tained,  insoluble  lead  selenate  is  precipitated  ;  this  salt  is 
decomposed  by  sulphuretted  hydrogen  yielding  dihydric  sele 
nate  and  lead  sulphide,  thus  : 

Pb  SeO4  +  H2  S=  H2SeO4  +  PbS. 

On  evaporating  the  liquid  obtained,  selenic  acid  is  left. 

Selenic  acid  decomposes  on  heating  into  selenic  dioxide, 
oxygen,  and  water  ;  the  metallic  selenates  correspond  to  the 
analogous  sulphates,  and  are  isomorphous  with  them,  that  is, 
they  crystallize  in  the  same  forms  and  have  an  analogous 
composition.  . 

Seleniuretted  Hydrogen,  or  Di-hydric  Selenide.  Symbol 
H2Se.  Combining  Weight  81-5.  Density  4075. 

This  gas  is  obtained  by  the  action  of  an  acid  upon  a 
selenide,  exactly  as  sulphuretted  hydrogen  is  prepared  from 
a  sulphide.  It  is  a  colorless  inflammable  gas,  possessing  a 
nauseous  smell,  and  exhibiting  properties  in  every  respect 
analogous  to  those  of  its  sulphur  representative.  The  most 
important  difference  between  the  two  elements,  sulphur  and 
Selenium,  is  that  the  former  is  oxidized  to  its  highest  point  by 
the  action  of  nitric  acid,  whereas  the  latter  requires  to  be 
fused  with  nitre  in  order  to  reach  the  corresponding  degree 
of  oxidation. 


Elementary  Chemistry.  119 


TELLURIUM.      Symbol  Te.      Combining    Weight   129. 
Density  129. 

Tellurium  (from  Tellus,  the  earth)  is  a  very  rare  substance, 
which,  although  resembling  a  metal  in  its  physical  properties, 
bears  so  strong  an  analogy  to  sulphur  and  selenium  in  its 
chemical  relations,  that  its  compounds  are  best  considered  in 
this  place.  It  occurs  combined  with  gold  and  other  metals 
in  Transylvania  and  Hungary.  The  specific  gravity  of  tellu 
rium  is  6*25,  and  it  exhibits  a  bright  white  metallic  lustre.  It 
melts  at  about  500°,  and  may  be  volatilized  at  a  white  heat  in 
a  current  of  hydrogen  gas.  When  heated  in  the  air  it  burns 
with  a  bluish-green  flame,  forming  white  fumes  of  telluric 
dioxide;  this  compound  is  also  formed  when  tellurium  is 
oxidized  by  nitric  acid,  and  the  solution  evaporated  to  dry- 
ness.  With  water  the  dioxide  forms  tellurous  acid,  H2  TeO3, 
and  with  metals  in  place  of  hydrogen,  tellurites  of  the  general 
form,  M9  TeO3.  When  tellurium  or  a  tellurite  is  fused  with 
nitre,  potassium  tellurate,  K->TeO.i,  is  formed,  from  which 
telluric  acid,  H2  TeO4  +  2H2O,  and  the  trioxide  TeO3  can  be 
obtained.  With  hydrogen,  tellurium  forms  a  colorless  gas, 
H2Te,  which  cannot  be  distinguished  by  its  smell  from 
sulphuretted  hydrogen. 

Oxygen,  sulphur,  selenium,  and  tellurium,  appear  to  form  a 
natural  group  of  elements,  each  uniting  with  two  atoms  of 
hydrogen  to  form  a  series  of  bodies  possessing  analogous 
properties,  viz.  H2O,  H2S,  H2Se,  H2Te.  The  last  three 
members  of  the  group  exhibit  the  same  kind  of  striking 
gradation  of  properties  as  was  noticed  in  the  case  of  chlorine, 
bromine,  and  iodine.  Thus  the  mean  of  the  combining 
weights  of  the  two  extremes  is  nearly  the  combining  weight 

of  the  mean  21_!£!    -*.  ^  .  whjlst  their  specific  gravities, 

2*0,  4-5,  and  6-25,  and  their  melting  and  boiling  points%how  a 
similar  gradation. 


I2O  -        Elementary  Chemistry. 


. 

SILICON'.     Symbol  Si.     Combining  Weight  =  28. 

Silicon,  next  to  oxygen,  is  the  most  abundant  element 
known.  It  does  not  occur,  however,  in  the  free  state,  but 
always  combined  with  oxygen  to  form  silicic  dioxide  (silicic 
acid,  or  silica).  Silicic  dioxide  exists  nearly  pure  in 
quartz  or  rock  crystal,  in  flint,  sand,  and  in  a  variety  of 
minerals.  Silicon  also  occurs  combined  with  metals  and  oxy 
gen,  forming  metallic  silicates  ;  and  of  these  the  greater 
part  of  almost  all  known  rocks,  especially  the  primary  rocks, 
is  composed. 

In  order  to  obtain  silicon  in  the  free  state,  a  compound  of 
this  substance  with  fluorine  and  potassium  is  heated  with 
metallic  potassium  ;  a  violent  reaction  occurs,  and  when  the 
contents  of  the  tube  in  which  the  decomposition  was  effected 
are  put  into  water,  silicon  is  left  undissolved  in  the  form  of  a 
brown  amorphous  powder.  Silicon  can  be  obtained  in  three 
different  modifications  —  amorphous,  crystalline,  and  graphi- 
toidal,  corresponding  to  the  modifications  of  carbon.  The 
graphite  form  of  silicon  is  prepared  by  heating  the  brown 
amorphous  powder  to  a  high  temperature,  when  the  mass 
contracts,  and  becomes  much  more  dense.  Crystalline  silicon 
is  best  obtained  by  fusing  the  mixture  which  gives  brown  silicon 
with  zinc  :  on  cooling  the  mass,  crystals  of  silicon  are  found 
to  be  deposited  on  the  zinc,  which  latter  can  easily  be  re 
moved  by  solution  in  an  acid.  Silicon  thus  obtained  is  hard 
enough  to  scratch  glass  ;  it  has  a  specific  gravity  of  2-49, 
and  maybe  fused  at  a  temperature  between  the  melting  points 
of  cast  iron  and  steel. 

Silicic  Dioxide,  or  Silica,  Symbol  Si  Oa,  Combining  Weight 
60,  is  the  only  known  oxide  of  silicon  ;  it  occurs  in  the  pure 
state  crystallized  in  six-sided  prisms  or  pyramids,  as  quartz, 
and  exists  in  a  less  pure  condition  in  sandstone,  chalcedony, 
flint,  anj  agate,  &c.  The  aluminium-,  potassium-,  calcium-, 
and  iron-silicates,  mixed  together  in  different  proportions, 
constitute  a  large  number  of  minerals. 

Crystallized  silica,  in  the  form  of  white  transparent  quartz, 


Elementary  Chemistry.  12  1 

has  a  specific  gravity  of  2*6,  and  is  hard  enough  to  scratch 
glass  ;  it  is  unattacked  and  undissolved  by  all  acids  with  the 
exception  of  hydrofluoric  acid,  by  the  action  of  which  silicic 
tetrafluoride  and  water  are  produced,  thus  : 


Silica  is  infusible  except  at  the  highest  temperature  of  the 
oxyhydrogen  blowpipe,  when  it  melts,  to  a  colorless  globule. 
Silica  in  an  amorphous  condition  can  also  be  prepared,  and 
then  exhibits  peculiar  properties.  For  this  purpose  one  part 
of  finely  divided  quartz  or  white  sand  is  heated  with  four 
parts  of  sodium  carbonate  ;  as  soon  as  the  latter  begins  to 
fuse,  the  silica  combines  with  the  sodium  and  oxygen  con 
tained  in  the  carbonate,  carbonic  acid,  CO2,  being  evolved 
with  effervescence,  owing  to  the  formation  of  a  sodium  sili 
cate.  If  the  fused  mass  be  boiled  with  water,  it  will  dissolve, 
and  on  the  addition  of  hydrochloric  acid,  silicic  acid,  H4  SiO-t. 
partly  separates  as  a  gelatinous  mass,  partly  remains  dis 
solved  in  the  liquid.  If  this  solution  be  evaporated  to  dry- 
ness  and  heated  a  little,  and  hydrochloric  acid  then  added, 
silicic  dioxide  is  left  as  a  white  powder  insoluble  in  acids  ; 
this  amorphous  silica  possesses  a  specific  gravity  of  2'2  to 
2-3,  and  can  only  be  obtained  again  in  solution  by  repeating 
the  process  of  fusion  with  an  alkali,  &c.  A  pure  aqueous 
solution  of  hydric  silicate  can  be  obtained  by  allowing  the  so 
lution  of  this  substance  in  hydrochloric  acid  to  dialyse,  or 
diffuse  through  a  membrane,  for  some  days.  All  the  hydro 
chloric  acid  and  soluble  chlorides  in  this  solution  being  crys 
talloids  pass  through  the  dialyser,  while  the  colloidal  hydric 
silicate  remains  behind  in  solution  :  the  limpid  solution  thus 
obtained  may  be  concentrated  by  boiling  until  the  quantity  of 
hydric  silicate  in  solution  reaches  14  per  cent.  :  but  this  solu 
tion  is  apt  to  gelatinize  on  standing,  forming  a  transparent 
jelly-like  mass. 

Potassium  and  sodium  silicates  are  largely  used  for  various 
purposes  in  the  arts,  whilst  a  mixture  of  these  with  calcium, 
iron,  and  lead  silicates,  forms  the  several  descriptions  of 

6 


122 


Elementary  Chemistry. 


glass  (p.  ).  Some  remarkable  compounds  of  silicon  with 
oxygen  and  hydrogen  have  lately  been  discovered,  but  their 
composition  has  not  yet  been  accurately  determined.  A  com 
pound  of  silicon  and  hydrogen  termed  Siliciuretted  Hydrogen 
is  also  known  :  it  has,  however,  not  been  obtained  in  the  pure 
state  ;  it  is  colorless,  and  takes  fire  on  coming  into  contact 
with  the  air,  forming  silica  and  water. 

Silicic  Tetra-chloride.  Symbol  SiCU.  Combining  Weight 
170.  Density  85. 

This  compound  is  formed  when  silicon  is  heated  in  chlo 
rine,  but  may  be  prepared  by  passing  dry  chlorine  over  a 
red-hot  mixture  of  finely-divided  silica  and  carbon.  Chlo 
rine  alone  is  not  able  to  decompose  silica,  but  in  presence 
of  carbon  a  change  is  effected,  carbonic  oxide  being  at  the 
same  time  formed. 

Si02  +  C14  +  C2  =  SiCh  +  2CO. 

Silica,  chlorine,  and  carbon  yield  silicic  tetrachloride  and 
carbonic  oxide.  Fig.  36  shows  the  arrangement  employed 


FIG.  36. 

for  preparing  this  body ;  the  mixture  of  silica  and  carbon  is 
placed  in  a  porcelain  tube,  which  can  be  strongly  heated  by 
the  furnace  ;  dry  chlorine  gas  is  passed  through  the  tube,  and 
the  volatile  silicic  tetrachloride  collects  in  the  cooled  tube. 
Silicic  tetrachloride  is  a  volatile  colorless  liquid,  boiling  at 
59°  C,  and  having  a  specific  gravity  of  1*52.  It  is  at  once 


Elementary  Chemistry.  123 

decomposed  by  water,  silicic  and  hydrochloric  acids  being 
formed  ;  hence  we  may  see  that  this  body  in  the  chlorine  series 
corresponds  to  silicic  dioxide  in  the  oxygen  series,  and  that 
in  the  formation  of  the  chloride  four  atoms  of  chlorine 
simply  replace  its  equivalent  quantity,  two  atoms  of  oxygen, 
in  the  silica  :  SiO2  becomes  SiCl4,  as  one  atom  of  oxygen  is 
equivalent  to  two  of  chlorine. 

Silicic  Tetra-fluoride.  Symbol  SiF4.  Combining  Weight 
104.  Density  52. 

This  is  one  of  the  most  singular  compounds  of  silicon  ;  it 
is  formed  whenever  free  hydrofluoric  acid  comes  in  contact 
with  either  free  or  combined  silica ;  this  is  the  cause  of  the 
etching  which  hydrofluoric  acid  exerts  upon  glass.  Silicic 
tetrafluoride  is  best  prepared  by  heating  in  a  flask  equal  parts 
by  weight  of  finely-powdered  fluor  spar,  and  white  sand,  with 
about  eight  parts  of  sulphuric  acid :  the  decomposition  first 
occurring  is  the  one  by  which  hydrofluoric  acid  is  generated, 
and  this  then  attacks  the  silica,  thus  : 

1)  CaF2  +  H2SO4  =  CaSO4  +  2HF. 

2)  4HF   +  Si03      =    2H2O  +  SiF4. 

Silicic  tetrafluoride  is  a  colorless  gas  which  fumes  strongly 
in  the  air  ;  it  does  not  burn  nor  support  combustion,  and  may 
be  condensed  by  great  pressure,  or  exposure  to  a  very  low 
temperature,  to  a  colorless  liquid ;  it  is  decomposed  by  water, 
but  may  be  collected  over  mercury,  or  by  displacement ;  when 
led  into  water  this  gas  yields  hydric  silicate,  which  is  depos 
ited  in  a  state  of  fine  division,  and  a  new  acid  called  hydro- 
fluo-silicic  acid,  or  hydric  .silico-fluoride,  having  the  composi 
tion  H2  Si  F6,  which  remains  in  solution.  This  substance  has 
an  acid  reaction  ;  the  corresponding  potassium-  and  barium 
silico-fluorides  (K2SiF6  and  Ba  SiF6)  are  insoluble  in  water 
and  alcohol. 


BORON.     Symbol's.     Combining  Weight  iro. 

Boron  combined  with  oxygen  and  sodium  is  found  as  borax 
in  nature  ;  it  is  also  found  combined  with  oxygen  alone  as 


124  Elementary  Chemistry. 

boracic  trioxide  (boracic  acid).  It  exists,  like  carbon  and 
silicon,  in  three  forms— crystalline,  graphitoidal,  and  amor 
phous.  Boron  is  easily  obtained  as  a  gray  amorphous  pow 
der,  by  heating  fused  boracic  trioxide,  B2O3,  with  sodium. 
Crystallized  boron  is  prepared  by  heating  the  amorphous  form 
strongly  with  aluminium — this  metal  in  the  fused  state  having 
the  property  of  dissolving  boron,  which  separates  out  in 
nearly  colorless  crystals  when  the  metal  cools,  just  as  the 
graphitoidal  form  of  carbon  does  from  its  solution  in  iron  on 
cooling  (p.  68).  Scales  of  graphitoidal  boron  are  also  formed 
in  this  way.  Crystallized  boron  has  a  specific  gravity  of  2*68, 
and  occurs  in  the  form  of  octahedra,  which  are  hard  enough 
to  scratch  the  ruby.  In  one  specimen  of  these  colorless  crys 
tals  which  were  analyzed,  some  quantity  of  carbon  was  found 
to  be  present ;  hence  carbon  may  be  said  to  have  been  pre 
pared  artificially  in  the  diamond  modification.  Boron  burns 
when  strongly  heated  in  oxygen  or  in  chlorine,  forming  the 
oxide  or  chloride  ;  it  is  remarkable  as  uniting  with  nitrogen 
by  direct  combination — in  this  respect  resembling  certain 
metals,  such  as  titanium. 

Boracic  Trioxide  (commonly  called  Boracic  acid}.  Symbol 
B2O3.  Combining  Weight  70-0. 

In  certain  old  volcanic  districts  in  Tuscany  constant  jets 
of  steam  and  gas  escape  from  the  earth.  These  steam  jets, 
which  are  known  as  fumerolles  or  sojfioni,  contain  small 
quantities  of  boracic  acid,  HBOa  +  HaO,  which  collect  in  the 
lagoons  formed  at  the  mouth  of  the  jet.  By  means  of  the 
heat  of  natural  steam  jets,  the  solution  of  boracic  acid  is 
concentrated,  and  the  acid  obtained  by  crystallization  ; 
about  2,000  tons  of  crude  acid  thus  prepared  are  imported 
every  year  from  Tuscany.  Boron  likewise  occurs  in  tinkal  or 
borax  in  Thibet,  and  as  boracic  trioxide  on  the  coast  of  Cali 
fornia. 

Real  boracic  acid  is  obtained  by  decomposing  a  hot  solution 
of  borax,  Na2  B4O7,  with  sulphuric  acid ;  crystals  separate 
out  on  cooling,  having  the  composition  H  BO2  +  HaO. 
These  crystals  on  heating  lose  water  and  pass  into  a  fused 


Elementary  Chemistry.  125 

glassy  mass,  consisting  of  boracic  trioxide,  B2O3.  Boracic 
acid  is  slightly  soluble  in  cold,  and  rather  more  soluble  in  hot 
water  ;  it  imparts  a  peculiar  green  tint  to  the  blowpipe  flame, 
which  exhibits  a  characteristic  series  of  bands  when  examined 
by  means  of  the  spectroscope.  Metallic  Borates  are  known, 
and  likewise  several  combinations  of  these  borates  with 
boracic  trioxide.  Thus  sodium  borate,  or  boracic  acid  in 
which  the  atom  of  hydrogen  is  replaced  by  sodium,  is  Na  BO2 
+  4H2O  ;  whilst  fused  borax  is  this  salt  combined  with  one 
molecule  of  boracic  trioxide,  thus  :  2  Na  BO2  +  B2O3,  or  Naa 
B4O7.  Compounds  similar  to  this  latter  salt  are  known 
amongst  the  sulphates.  Thus  Nordhausen  sulphuric  acid  is 
KUSO*  +  SO3,  and  a  sodium  compound,  Na2  SO4  +  SO3,  is 
known.  Many  of  the  metallic  oxides  are  soluble  in  fused 
borax,  giving  colored  glasses.  Hence  this  compound  is 
largely  used  in  the  arts  as  a  flux,  and  in  the  laboratory  as  a 
blowpipe  re-agent. 

Boron  combines  with  chlorine  to  form  a  trichloride,  BC13, 
and  with  fluorine  to  form  a  corresponding  trifluoride,  BF3 ; 
both  these  compounds  are  prepared  by  a  method  similar  to 
that  adopted  for  the  corresponding  silicon  compounds,  to 
which,  notwithstanding  their  slightly  different  constitution, 
they  bear  a  strong  resemblance.  Like  silicon  also,  boron 
forms  a  borofluoride  :  hydrofluoboric  acid  (or  hydric  boro- 
fluoride),  is  HBF4,  and  potassium  borofluoride,  KBF4. 


LESSON  XV. 

PHOSPHORUS.     Symbol?.     Combining  Weight  31.     Vapor 
Density  62* 

Phosphorus  does  not  occur  free  in  nature,  but  is  found  in 
combination  with  oxygen  and  calcium  in  large  quantities  in 

*  The  volume  occupied  by  the  atom  of  phosphorus  weighing  31  is  only  half  as 
large  as  that  occupied  by  the  atoms  of  each  of  the  preceding  elements :  hence  the 
atomic  volume  of  phosphorus  is  i,  that  of  the  preceding  elements  being  i. 


126  Elementary  Chemistry. 

the  bodies,  and  especially  the  bones,  of  animals,  and  in  the 
seeds  of  plants.  When  bones  are  burnt,  a  white  solid  mass 
is  left  behind ;  this  is  called  Calcium  Phosphate  (phosphate 
of  lime).  Animals  obtain  the  phosphate  necessary  for  the 
formation  of  their  tissues,  &c.,  from  plants.  Plants,  again, 
draw  their  supply  from  the  soil,  whilst  soils  derive  their  phos 
phate  from  small  quantities  existing  in  the  oldest  granite  rocks, 
by  the  disintegration  of  which  the  fertile  soils  have  been  pro 
duced.  Phosphorus  appears  also  to  be  a  very  necessary 
ingredient  in  the  brain  and  other  centres  of  the  nervous 
action.  It  was  accidentally  discovered  by  Brand  of  Ham 
burg  in  1669;  but  Scheele,  in  1769,  pointed  out  the  existence 
of  phosphorus  in  the  bones,  and  examined  its  properties  care 
fully. 

Phosphorus  is  prepared  from  powdered  bone-ash,  by  mix 
ing  it  with  two-thirds  of  its  weight  of  sulphuric  acid  and  15  to 
20  parts  of  water.  The  sulphuric  acid  decomposes  the  bone- 
ash,  forming  calcium  sulphate,  or  gypsum,  which  separates 
out  as  a  white  insoluble  powder  ;  whilst  the  greater  part  of 
the  phosphorus  in  the  bones  comes  into  solution  in  combina 
tion  with  calcium,  oxygen,  and  hydrogen,  forming  a  salt,  com 
monly  known  as  superphosphate  of  lime.  The  liquid  is  drawn 
off  clear,  evaporated  down  to'  a  syrup,  and  then  mixed  with 
powdered  charcoal,  dried,  and  heated  to  redness  in  an  earthen 
ware  retort,  the  neck  of  which  dips  under  water.  The  super 
phosphate  may  be  considered  to  contain  phosphoric  pentoxide, 
P2O6,  from  which  the  carbon  takes  away  the  oxygen,  forming 
carbonic  oxide,  and  liberating  phosphorus,  which  distils  over 
and  condenses  under  water  in  yellow  drops. 

Phosphorus  is  an  exceedingly  inflammable  and  oxidizable 
substance,  and  requires  great  care  in  its  preparation ;  it  is 
manufactured  on  a  very  large  scale  for  making  the  composi 
tion  for  the  tips  of  lucifer  matches.  In  order  to  purify  the 
phosphorus  thus  prepared,  it  may  again  be  distilled,  or  pressed 
when  melted  under  hot  water  through  leather ;  it  is  then  cast 
into  sticks  and  kept  under  cold  water.  Phosphorus  is  a 
slightly  yellow  semitransparent  solid,  resembling  white  wax 


Elementary  Chemistry.  127 

both  in  appearance  and  consistency ;  but  at  low  temperature 
it  becomes  brittle.  Its  specific  gravity  is  1*83,  and  it  melts  at 
44°,  forming  a  transparent  liquid  ;  it  boils  at  290°,  giving  rise 
to  a  colorless  gas.  In  the  air  it  gives  off  white  fumes,  emit 
ting  a  pale  phosphorescent  light  in  the  dark — whence  its  name 
(0wj  light,  and  0epu,  I  bear  ;  lucifer,  from  lux,  light,  and/m?, 
I  bear,  is  its  literal  Latin  equivalent)  ;  it  is  then  undergoing 
a  slow  combustion,  the  white  fumes  consisting  of  trioxide. 
At  a  temperature  very  little  above  its  fusing  point  phosphorus 
takes  fire  in  the  air,  entering  into  active  combustion,  and 
forming  phosphoric  pentoxide,  P2O5  (phosphoric  anhydride). 
The  ignition  of  phosphorus  takes  place  by  slight  friction,  or 
by  a  blow,  and  even  the  heat  of  the  hand  may  cause  this  sub 
stance  to  ignite  ;  hence  great  care  must  be  taken  in  handling 
phosphorus,  and  it  should  always  be  cut  under  water.  Phos 
phorus  does  not  dissolve  in  water,  alcohol,  or  ether,  but  it  is 
slightly  soluble  in  oils,  and  very  readily  soluble  in  carbonic 
disulphide,  crystallizing  from  its  solution  in  this  liquid  in 
rhombic  dodecahedra. 

If  yellow  phosphorus  be  exposed  to  a  temperature  of  about 
240°  for  some  hours  in  an  atmosphere  incapable  of  acting 
chemically  on  it  (such  as  hydrogen  or  carbonic  acid),  it  is 
found  to  have  undergone  a  very  remarkable  change,  being 
wholly  converted  into  a  dark  red  opaque  substance  altogether 
insoluble  in  carbonic  disulphide.  The  weight  of.red  substance 
produced  is  exactly  equal  to  that  of  yellow  phosphorus  used. 
This  is  called  Red,  or  Amorphous  Phosphorus,  and  differs 
much  in  its  properties  from  the  yellow  modification,  especially 
in  its  inflammability,  as  it  does  not  take  fire  in  the  air  until 
heated  to  above  260°,  when  it  becomes  reconverted  into  the 
ordinary  form  and  burns  with  the  formation  of  phosphoric 
pentoxide.  The  specific  gravity  of  amorphous  phosphorus  is 
2*14.  The  sudden  conversion  of  yellow  into  red  phosphorus 
can  be  shown  by  heating  a  small  piece  of  ordinary  phosphorus 
in  a  dry  tube  with  a  mere  trace  of  iodine ;  combination  at 
once  occurs,  a  small  trace  of  volatile  phosphoric  iodine  is 
formed,  and  the  remainder  of  the  phosphorus  is  converted 


128  Elementary  Chemistry. 

into  the  red  modification.  The  red  or  amorphous  modification 
of  phosphorus  can  also  be  obtained  in  a  crystallized  form  by 
heating  red  phosphorus  in  a  tube  with  metallic  lead.  The 
phosphorus  dissolves  in  the  melted  lead,  and  on  cooling 
separates  out  in  crystals,  which  possess  a  bright  black  metallic 
lustre,  and  have  a  specific  gravity  of  2-34. 

Phosphorus  forms  two  oxides,  phosphoric  trioxide,  P2O3, 
and  phosphoric  pentoxide,  P2O5. 

Phosphoric  Trioxide,  or  Phosphorous  Anhydride.  Sym 
bol  P2O3.  Combining  Weight  no. 

This  oxide  is  formed  when  phosphorus  is  burnt  in  a  limited 
current  of  dry  air  when  it  undergoes  slow  combustion.  It 
forms  a  white  non-crystalline  powder  which  combines  with 
great  energy  with  water,  forming  thereby  phosphorous  acid, 
or  hydric  phosphite,  H3PO3.  This  acid  is  likewise  formed 
when  phosphorus  is  allowed  gradually  to  oxidize  in  moist  air, 
and  also  by  the  action  of  phosphoric  trichloride  on  water, 
thus  : 

PC13  +  3H2O  =  H3PO3  +  3HC1. 

Phosphoric  trichloride  and  water  give  hydricphosphite  and 
hydrochloric  acid. 

By  boiling  this  solution  the  hydrochloric  acid  is  driven  off, 
and,  on  cooling,  crystals  of  phosphorous  acid  are  deposited. 
There  are  two  classes  of  metallic  phosphites — the  one  con 
tains  those  which  correspond  to  phosphorous  acid  in  which 
two  atoms  of  hydrogen  have  been  replaced  by  metal ;  and  the 
second  containing  those  in  which  one  atom  only  of  hydro 
gen  has  been  thus  replaced  :  the  general  forms  of  the  two 
will  therefore  be  M2H  PO3  and  MH2  PO3,  the  letter  M  de 
noting  an  atom  of  a  monatomic  metal. 

Phosphoric  Pentoxide  (Phosphoric  Anhydride).  Symbol 
P2O6.  Combining  Weight  142. 

This  substance  is  formed  when  phosphorus  burns  brightly 
in  excess  of  air  or  oxygen  ;  it  is  a  white  amorphous  light 
powder,  which  absorbs  moisture  with  the  utmost  avidity, 
forming  hydric  phosphate  or  phosphoric  acid,  H3  PO4  ;  it  is 
for  this  reason  frequently  used  in  the  laboratory  for  the  pur- 


Elementary  Chemistry.  129 

pose  of  drying  gases.  Phosphoric  pentoxide  is  volatile,  and 
may  be  sublimed  unchanged  by  heating  in  a  test  tube.  It 
can  be  best  prepared  by  burning  small  pieces  of  phosphorus 
placed  one  by  one  in  a  cup  hung  in  the  centre  of  a  large  dry 
glass  globe,  and  blowing  in  a  sufficient  supply  of  dry  air  by 
means  of  a  bellows  or  aspirator.  The  white  powder  falls 
down,  and  may  be  shaken  out  of  the  globe  when  the  operation 
is  completed. 

Trihydric  Phosphate  (Tribasic  Phosphoric  Acid).  Symbol 
H3  PO4.  Combining  Weight  98. 

When  the  preceding  compound  is  brought  into  contact 
with  water,  great  heat  is  evolved,  and  combination  takes 
place  with  a  hissing  noise.  If  the  solution  be  boiled,  trihy- 
dric  phosphate  is  found  in  solution,  being  formed  thus  : 

P2O6  +  3  H2O  =  2(H3  PO4). 

Phosphoric  pentoxide  and  water  give  trihydric  phosphate. 

The  corresponding  calcium  salt,  Cas  2PO4,  occurring  in 
bone-ash  and  in  many  minerals,  constitutes  the  main  source 
of  all  the  phosphorus  compounds.  Trihydric  phosphate  is 
also  formed  when  phosphorus  is  heated  with  nitric  acid  :  the 
lower  oxides  of  nitrogen  are  given  off  as  red  fumes,  and  the 
phosphorus  gradually  disappears  ;  by  evaporating,  and  boil 
ing  the  colorless  liquid,  trihydric  phosphate  may  be  obtained. 
The  same  substance  is  procured  directly  from  bone-ash  by 
frequent  addition  of  sulphuric  acid  and  continued  evapora 
tion  :  gypsum  gradually  separates  out,  leaving  a  solution 
from  which  hydric  phosphate  can  be  obtained  by  neutralizing 
with  ammonium  carbonate,  filtering,  evaporating  to  dryness 
the  clear  liquid  thus  obtained,  and  igniting  the  residue.  If 
sodium  carbonate  be  added  to  a  solution  of  trihydric  phos 
phate,  effervescence  will  at  once  ensue  from  the  liberation  of 
carbonic  acid,  and  if  the  carbonate  be  added  until  the  solu 
tion  ceases  to  redden  litmus  paper,  a  salt  will  be  obtained  on 
evaporation  which  crystallizes  in  large  transparent  prisms. 
This  is  rhombic or common  neutral  sodium  phosphate  j  its  com 
position  is  represented  by  the  symbol  Na2H  PO4,  with  twelve 


130  Elementary  Chemistry. 

atoms  of  water  of  crystallization.  If  caustic  soda  be  added  to 
a  solution  of  this  common  phosphate,  a  salt  termed  the  sub- 
phosphate  crystallizes  out  in  small  needles  on  evaporation  : 
the  composition  of  this  salt  is  Nas  PO4  with  twelve  atoms  of 
water  of  crystallization  ;  and  if  phosphoric  acid  be  added  to  a 
solution  of  common  phosphate,  the  so-called  Sodium  super 
phosphate  is  formed,  NaH2PO4.  We  have  therefore  the 
following  tribasic  hydric  and  sodium  phosphates  : 

Trihydric  Phosphate V  H3  PO4 

Dihydric  Sodium  Phosphate      .     .     .  HaNa  PO4 

Hydric  di-Sodium  Phosphate     .     .     .  H  Naa  PO4 

Tri-Sodium  Phosphate Naa  PO4 

All  these  substances  are  distinguished  by  giving  a  yellow 
precipitate  with  solution  of  silver  nitrate  consisting  of  tri-sil- 
ver  phosphate,  Ag3PO4  ;  and  by  producing  with  ammonia 
and  magnesium  sulphate  a  white  crystalline  precipitate  of 
ammonium  magnesium  phosphate,  (NH4)  Mg  PO4.  Small 
traces  of  phosphates  can  readily  be  detected  by  the  yellow 
precipitate  which  forms  in  nitric  acid  solution  of  ammonium 
molybdate.  The  three  atoms  of  hydrogen  in  trihydric  phos 
phate  may  be  replaced  by  three  different  metals  ;  thus, 
Microcosmic  Salt  is  Hydric-sodium-ammonium  Phosphate, 
H  Na  NH4  PO4. 

If  common  sodium  phosphate  be  heated  to  redness,  water 
is  driven  off,  and  a  compound  called  Sodium  Pyrophosphate 
remains,  having  the  composition  Na4  P2O7,  two  molecules  of 
neutral  phosphate  yielding  one  of  pyrophosphate,  thus  : 

2.  Naa  H  PO4  =  H2O  +  Na4  PaO7. 

When  this  salt  is  dissolved  in  water,  it  can  be  recrystal- 
lized,  and  does  not  take  up  water  again  so  as  to  pass  back  to 
the  state  of  common  phosphate  (except  on  long-continued 
boiling  of  its  solution).  This  substance  gives  with  silver 
nitrate  a  white  precipitate  of  silver  pyrophosphate,  Ag4  PaO7, 
and  thus  this  class  of  phosphates  may  be  distinguished  from 


Elementary  Chemistry.  131 

the  preceding  or  tribasic  phosphates.  A  so-called  acid 
sodium  pyrophosphate,  having  the  composition  Na2Ha  PaOr, 
is  also  known. 

If  microcosmic  salt.  Na  (NH4)  H  PO4,  is  heated,  water  and 
ammonia  are  driven  off,  and  a  substance  called  Sodium 
metaphosphate,  Na  PO8,  is  left ;  this  dissolves  unaltered  in 
water",  forming  one  of  a  third  class  of  phosphates  termed 
monobasic  phosphates,  or  metaphosphates.  The  solutions  of 
these  salts  may  be  distinguished  from  those  of  the  two  pre 
ceding  classes  of  salts  by  their  producing  gelatinous  precipi 
tates  with  solutions  of  calcium  and  silver  salts  consisting  of 
the  metaphosphates  of  these  metals.  Monohydric  phosphate 
(or  metaphosphoric  acid),  HPO3,  is  obtained  in  the  form  of 
a  transparent  icelike  mass  by  evaporating  the  solution  of 
trihydric  phosphate  and  igniting  the  residue.  On  dissolving 
this  glacial  acid  in  cold  water,  a  solution  of  monohydric  phos 
phate  is  obtained,  but  this,  on  boiling,  changes  to  the  tri 
hydric  phosphate. 

From  the  above  it  is  seen  that  three  modifications  of  phos 
phoric  acid  are  known,  or  rather,  three  different  acids,  each 
giving  rise  to  a  class  of  metallic  salts.  Thus  we  have — 

(1)  Tri-hydric  phosphate,  or  phosphoric  acid,  H3  PO4,  and 
tri-sodium  phosphate,  Na3  PO4. 

(2)  Tetra-hydric  pyrophosphate,  or   pyrophosphoric  acid, 
H4P2O7,  and  sodium  pyrophosphate,  Na4  PaO7. 

(3)  Mono-hydric  phosphate,  or  metaphosphoric  acid,  HPO3, 
and  sodium  metaphosphate,  Na  PO3. 

Each  of  the  above  hydric  phosphates  can  be  prepared  by 
passing  sulphuretted  hydrogen  through  water  containing  in 
suspension  the  corresponding  silver  salts  ;  thus  : 

(1)  2(Ag3P04)  +  3(H2S)    =  2(H3  P04)   +  3(Ag2  S). 

(2)  Ag4P2O7      +  2(H2S)    =      H4  P2O7   +   2(Ag2  S). 

(3)  2(Ag  PO3)  +    (HaS)    =  2(HPO3)     +  Ag2S 

In  addition  to  the  phosphates  and  phosphites,  a  class  of 
salts  termed  Hypophosphites  is  also  known  :  the  composition 
of  hydric  hypophosphite  is  represented  by  the  formula 


132  Elementary  Chemistry. 

H  PH2O2,  and  that  of  sodium  hypophosphite  by  NaPH2O2  ; 
and  these  salts  may  be  supposed  to  be  hydric  or  sodium  me- 
taphosphate,  HPO3,  and  Na  PO3,  in  which  one  atom  of  oxy 
gen  has  been  replaced  by  its  equivalent,  or  two  atoms  of  hy 
drogen.  Sodium  hypophosphite  is  obtained  by  acting  with 
caustic  soda  on  phosphorus,  when  phosphuretted  hydrogen 
gas  is  evolved,  and  a  solution  of  hypophosphite  remains 
behind. 

Phosphorus  and  Hydrogen.  Three  compounds  of  phos 
phorus  and  hydrogen  are  known  —  PH3,  a  gas  ;  PH2  (or 
P2H4),  a  liquid  ;  and  P2H  (or  P4  H2),  a  solid  substance. 

Phosphuretted  Hydrogen.  Symbol  PH3.  Combining 
Weight  34.  Density  17. 

This  gas  is  obtained  in  the  pure  state  by  the  decomposition 
of  hydric  phosphite,  or  hydric  hypophosphite,  but  it  is  gen 
erally  prepared  by  the  action  of  caustic  potash  on  phos 
phorus. 

3KHO  +  P4  +  3H20  =  3  KPH202 


Caustic  potash,  and  phosphorus,  and  water,  give  potassium 
hypophosphite  and  phosphuretted  hydrogen. 

Each  bubble  of  the  gas  thus  prepared  takes  fire  spon 
taneously  on  coming  into  contact  with  the  air,  forming  sin 
gular  rings  of  phosphoric  pentoxide,  which  expand  as  they 
rise.  This  self-inflammability  of  the  gas  depends  upon  the 
presence  of  small  quantities  of  the  liquid  hydride  P2H4,  which 
may  be  condensed  to  a  volatile  and  very  inflammable  liquid 
by  passing  the  gaseous  hydride  through  a  tube  cooled  by  a 
freezing  mixture.  Pure  phosphuretted  hydrogen  prepared 
from  hydric  phosphite  by  heat,  does  not  undergo  spontaneous 
combustion  in  the  air.  This  mode  of  formation  may  be  thus 
represented  : 

4(H3  PO3)  =  3(H3  PO4)  +  PH3. 

Hydric  phosphite  gives  trihydric  phosphate  and  phos 
phuretted  hydrogen. 

There  is  some  doubt  about  the  exact  formulae  of  the  other 
two  hydrides  :  the  formulae  P2H4  and  P4H2,  are  in  accordance 


Elementary  Chemistry.  133 

with  their  physical  states,  and  are,  on  certain  other  theoret 
ical  grounds,  to  be  preferred  to  PH2  and  P2H. 

Phosphorus  and  Chloride.  Two  chlorides  of  phosphorus 
are  known — Phosphoric  trichloride,  PC13  and  Phosphoric 
pentachloride,  PC15.  The  first  of  these  is  a  colorless  strong 
ly  fuming  liquid,  which  is  easily  formed  by  passing  a  current 
of  chlorine  gas  over  phosphorus  contained  in  a  retort  :  when 
thrown  into  water  it  sinks  down  as  a  heavy  oil,  but  is  gradually 
decomposed,  hydric  phosphite  and  hydrochloric  acid  being 
formed  (see  p.  128).  The  specific  gravity  of  the  trichloride  is 
i -45,  and  its  boiling  point  is  73°'8.  Phosphoric  trichloride 
rapidly  absorbs  chlorine  gas,  and  is  converted  into  the  penta 
chloride,  a  yellowish  solid  substance,  which  is  also  formed 
when  phosphorus  is  burnt  in  an  excess  of  chlorine.  Phos 
phoric  pentachloride  is  decomposed  in  presence  of  excess  of 
water,  forming  trihydric  phosphate  and  hydrochloric  acid  ; 
but  when  only  a  limited  quantity  of  water  is  present,  a  liquid 
termed  phosphoric  oxichloride  is  formed,  having  the  composi 
tion  PClaO,  and  boiling  at  110°.  Corresponding  compounds 
with  bromine  are  likewise  known.  With  sulphur,  phosphorus 
forms  several  compounds,  and  it  is  an  interesting  fact  that 
two  of  these  compounds,  P2S3  and  P2S5,  correspond  in  com 
position  with  the  oxides  P2O3  and  P2O5.  The  oxide  cor 
responding  to  P2S,  however,  is  as  yet  unknown. 


LESSON  XVI. 

ARSENIC.     Symbol  As.     Combining  Weight  75.     Density  of 
Vapor  150.* 

Arsenic  closely  resembles  phosphorus  in  its  chemical  prop 
erties  and  in  those  of  its  compounds,  although  in  physical 

*  The  volume  occupied  by  an  atom  of  (gaseous)  arsenic  weighing  75  is  only  half 
of  that  occupied  by  the  other  elements  generally;  in  this  respect  arsenic  re 
sembles  phosphorus. 


134  Elementary  Chemistry. 

characters,  such  as  specific  gravity,  lustre,  &c.,  it  bears  a 
greater  analogy  to  the  metals  :  indeed,  it  may  be  considered 
the  connecting  link  between  these  two  divisions  of  the  ele 
ments,  antimony  and  bismuth  being  closely  connected  with  it 
on  the  one  hand,  and  phosphorus  and  nitrogen  on  the  other. 
Arsenic  is  sometimes  found  in  the  free  state,  but  more  fre 
quently  combined,  chiefly  with  iron,  nickel,  cobalt,  and  sul 
phur.  It  is  also  contained  in  very  small  quantities  in  many 
mineral  springs.  In  order  to  separate  arsenic  from  any  of  the 
metallic  ores  in  which  it  occurs,  the  ore  is  roasted,  or  exposed 
to  a  current  of  heated  air  in  a  reverberatory  furnace  ;  the  ar 
senic  combines  with  the  atmospheric  oxygen,  forming  arsenic 
trioxide  or  arsenious  oxide,  AsaOs.  which  is  carried  in  the 
state  of  vapor  from  the  furnace  into  long  chambers  or  flues  in 
which  the  trioxide  (commonly  known  as  arsenious  acid,  or 
white  arsenic)  is  deposited.  Metallic  arsenic  may  be  prepared 
from  this  oxide  by  mixing  it  with  charcoal  and  sodium  carbon 
ate,  and  heating  in  a  closed  crucible,  the  upper  part  of  which 
is  kept  cool  :  arsenic  condenses  in  the  cool  part  of  this  ap 
paratus  as  a  solid  with  a  brilliant  grayish  lustre.  It  tarnishes 
in  the  air  from  oxidation  ;  it  has  a  specific  gravity  of  57  to 
5'9,  and  when  heated  to  dull  redness,  it  volatilizes  as  a  color 
less  vapor  without  undergoing  fusion,  and  this  vapor  pos 
sesses  a  remarkable  garlic-like  smell.  Arsenic  when  heated 
in  the  air  takes  fire,  and  burns  with  a  bluish  flame,  forming 
arsenious  oxide,  As2  O3  ;  when  thrown  into  chlorine  it  in 
stantly  takes  fire,  forming  arsenic  trichloride,  AsCl3. 

Oxides  of  Arsenic.  Two  compounds  of  arsenic  and  oxy 
gen  are  known,  (i)  Arsenic  Trioxide  or  Arsenious  Oxide, 
AsoO3  (arsenious  acid  or  white  arsenic).  (2)  Arsenic  Pent- 
oxide  or  Arsenic  Oxide,  As2O6  (arsenic  anhydride). 

Arsenious  Trioxide.  Symbol  As2Os.  Combining  Weight 
198.  Density  (of  vapor)  198. 

This  substance  is  formed  when  arsenic  is  burnt  in  the  air 
or  in  oxygen,  but  it  is  generally  prepared  by  roasting  arsen 
ical  pyrites,  FeSAs  ;  its  specific  gravity  is  3-6.  It  exists  in 
two  distinct  forms,  the  crystalline  and  the  vitreous  ;  it  occurs 


Elementary  Chemistry.  135 

in  the  first  modification  crystallized  in  brilliant  octahedra,  and 
in  the  second  as  a  semi-transparent  glass-like  solid,  devoid  of 
crystalline  structure  :  this  form  of  the  substance,  on  standing, 
becomes  opaque  like  porcelain,  diminishing  in  specific  gravity. 
Arsenious  oxide  is  feebly  soluble  in  water  ;  the  solution 
(which  may  be  considered  to  contain  true  arsenious  acid  or 
trihydric  arsenic,  H3AsO3,  analogous  to  phosphorous  acid)  has 
a  feebly  acid  reaction  :  it  dissolves  more  readily  in  hydro 
chloric  acid,  and  is  freely  soluble  in  solutions  of  the  alkalies, 
arsenites  being  formed  of  the  general  form  M3AsO3 ;  thus, 
trisilver  arsenite  is  Ag3AsO3.  The  alkaline  arsenites  are 
soluble  in  water  ;  those  of  the  metals  of  the  alkaline  earths 
and  heavy  metals  are  insoluble  in  water.  Sodium  arsenite  is 
used  largely  in  calico  printing  ;  Scheele's  green  and  Emerald 
green  are  compounds  containing  arsenious  trioxide  and 
copper,  both  of  which  are  made  in  large  quantities  for  em 
ployment  as  a  pigment.  All  the  soluble  arsenites  are  dread 
fully  poisonous  ;  the  best  antidote  is  freshly  prepared  ferric 
hydrate  (hydrated  ferric  oxide),  or  magnesia,  which  form  inso 
luble  arsenites,  and  thus  prevent  the  poison  from  entering 
into  the  system.  When  heated  to  about  220°  C,  arsenious 
oxide  volatilizes  without  melting,  forming  an  inodorous  and 
colorless  vapor.  It  is  occasionally  met  with  crystallized  in 
long  needles  of  the  same  form  as  the  crystals  of  the  corre 
sponding  oxide  in  the  antimony  series  (see  p.  200). 

Arsenic  Pentoxide  or  Arsenic  Oxide  (arsenic  anhydride). 
Symbol  As2  O5.  Combining  Weight  230. 

This  oxide  is  obtained  by  acting  upon  the  trioxide  with 
nitric  acid,  evaporating  to  dryness,  and  heating  to  a  tempera 
ture  of  270°.  It  forms  a  non-crystalline  white  powder,  which, 
when  strongly  heated,  decomposes  into  As2O3  and  O2.  This 
powder  is  readily  dissolved  by  water,  and  the  solution  yields 
crystals  of  arsenic  acid,  or  trihydric  arsenate,  H3AsO4 :  the 
metallic  compounds  corresponding  to  this  are  called  arsen- 
ates,  and  resemble  the  corresponding  tribasic  phosphates 
(p.  130)  in  composition,  whilst  they  are  identical  with  them  in 
crystalline  form.  Thus  we  have, 


i'36  Elementary  Chemistry. 

Tri-Sodium  Arsenate      .      .  Na3AsO4  4-  H2O. 

Hydric  Di-Sodium  Arsenate  HNaaAsO4  +  i2  H2O. 

Di-hydric  Sodium  Arsenate  .  H2NaAsO4  +  H2O. 

Tri-hydric  Arsenate     .     .     .  H8AsO4. 

With  solutions  of  magnesium  and  ammonium  together,  solu 
ble  arsenates,  like  phosphates,  form  an  insoluble  precipitate, 
having  the  composition  NH4  Mg  AsO4  +  6H2O  (ammonium 
magnesium  arsenate).  The  arsenates  of  the  alkaline  metals 
are  soluble,  those  of  the  other  metals  insoluble  in  water. 
Trisilver  arsenal  is  a  characteristic  salt  of  a  brownish-red 
color,  whereas  trisilver  arsenz/V?  has  a  bright  yellow  tint. 
Arsenic  acid  acts  as  a  still  more  powerful  poison  than 
arsenious  acid. 

No  arsenates  corresponding  to  the  pyro-  and  metaphos- 
phates  have  been,  as  yet,  obtained  ;  compounds  having 
the  composition  H4  As2  O7,  and  H  AsO3  have  been  indeed 
prepared  by  heating  a  tribasic  salt ;  but  on  solution  in  water 
they  combine  again  with  it  and  present  only  the  characteris 
tics  of  the  tribasic  acid. 

Arsenic  and  Hydrogen.  Arseniuretted  Hydrogen.  Sym 
bol  AsH3.  Combining  Weight  78.  Density  39. 

This  compound,  which  corresponds  to  phosphuretted  hy 
drogen,  and  to  ammonia,  is  formed  by  decomposing  an  alloy 
of  arsenic  and  zinc  with  sulphuric  acid.  It  is  a  colorless  gas, 
possessing  a  fetid  odor  of  garlic,  and  acts  as  a  most  deadly 
poison,'  a  single  bubble  of  the  pure  gas  having  been  known 
to  act  fatally :  when  cooled  to  -  40°  it  condenses  to  a  color 
less  liquid.  Arseniuretted  hydrogen  burns  with  a  bluish 
flame  and  deposits  arsenic  upon  a  cold  body  held  in  the 
flame  :  below  a  red  heat  it  is  decomposed  into  arsenic  and 
hydrogen. 

Arsenic  unites  with  chlorine,  bromine,  and  iodine,  to  form 
arsenic  trichloride,  tribromide,  and  triiodide.  The  trichloride 
is  a  colorless  volatile  liquid,  boiling  at  132°,  which  decom 
poses  in  contact  with  water,  yielding  arsenious  and  hydro 
chloric  acids.  Three  sulphides  of  arsenic  are  known — 


Elementary  Chemistry.  137 

Arsenic  Bisulphide,  As2S2,  which  occurs  naturally  as  Real 
gar  ;  Trisulphide,  AsaSs,  also  occurring  in  nature  as  Orpi- 
ment ;  and  Pentasulphide,  As2S5.  Orpiment  may  be 
obtained  by  passing  a  stream  of  sulphuretted  hydrogen  gas 
through  the  acid  solution  of  the  corresponding  oxide,  when 
it  is  precipitated  as  a  yellow  powder.  The  arsenic  sulphides 
form  with  the  sulphides  of  the  alkaline  metals  compounds 
bearing  the  same  analogy  to  the  trisulphide  and  pentasul- 
phide  that  arsenites  and  arsenates  do  to  the  trioxide  and 
pentoxide  :  in  short,  these  compounds  are  sulphur  and  salts, 
the  arsenites  and  arsenates  being  oxysalts  ;  hence  they  are 
called  j^/^/^arsenites  and  jz^/zarsenates. 

Arsenic  possesses  characters  of  so  peculiar  a  kind,  that  its 
presence  even  in  very  minute  traces  can  be  detected  with 
certainty.  From  its  solutions  it  can  be  precipitated  as  sul 
phide,  by  the  aid  of  sulphuretted  hydrogen  :  and  this  sulphide, 
when  dried  and  fused  in  a  small  test  tube  with  a  mixture  of 
potassium  cyanide  and  sodium  carbonate,  yields  a  ring  of 
metallic  arsenic  :  on  heating,  the  metal  is  oxidized  to  the  tri 
oxide,  which  deposits  in  minute  octahedral  crystals.  These, 
when  boiled  with  water,  yield  a  solution  giving  a  bright  green 
precipitate  with  neutral  copper  solutions,  and  a  bright  yellow 
one  with  neutral  silver  salts.  Arsenic  in  solution  may  be  also 
detected  by  the  evolution-  of  arseniuretted  hydrogen,  on 
adding  .zinc  and  sulphuric  acid  to  the  solution  to  be  tested  : 
on  burning  the  gas,  arsenic  is  deposited  in  the  metallic  state 
upon  a  piece  of  cold  porcelain  held  in  the  flame.  This  mirror 
dissolves  in  solution  of  sodium  hypochlorite  ;  and  if  treated 
with  nitric  acid,  and  the  solution  neutralized,  yields  with  sil 
ver  nitrate  solution  a  red  precipitate  of  trisilver  arsenate. 
Many  compounds  of  arsenic  heated  on  charcoal  in  the  inner 
blowpipe  flame  give  a  garlic  odor  of  arsenic.  Solutions  con 
taining  arsenic  boiled  with  hydrochloric  acid  and  clean  cop 
per,  deposit  a  coating  of  arsenic  upon  the  copper:  this  coat 
ing,  on  drying  and  heating  in  a  test  tube,  gives  a  ring  or 
mirror  of  arsenic,  which  may  be  oxidized  to  trioxide  and 
tested  as  before.  By  these,  and  other  reactions,  the  pres- 


138  Elementary  Chemistry. 

ence  of  the  minutest'  portion  of  arsenic  may  be  detected  with 
certainty. 

The  general  chemical  analogy  between  nitrogen,  phos 
phorus,  and  arsenic,  is  well  seen  when  their  corresponding 
compounds  are  examined  ;  thus  the  hydrides,  oxides,  and 
chlorides,  have  an  analogous  composition. 

N2O3  N2O5  NH3  NC13  (?) 

P2O3  P2O5  PH3  PC13 

As,03  As2O6  AsH3  AsCl3 

These  three  elements  are  all  Triatomic,  that  is,  one  atom 
of  each  of  these  bodies  is  equivalent  to,  and  capable  of,  re 
placing  three  atoms  of  hydrogen.  Antimony  and  bismuth 
(see  pp.  199,  201)  exhibit  in  their  chemical  relations  a  striking 
resemblance  to  the  foregoing  group. 

Atomicity  of  the  Elements. 

If  we  compare  together  the  compounds  of  the  preceding 
elements  with  hydrogen,  we  find  that  the  molecule  of 
certain  of  these  compounds  contains  one  atom  of  hydrogen  ; 
that  is  to  say,  the  combining  weight  (or  two  volumes)  of  the 
compound  contains  the  combining  weight  (or  one  volume)  of 
hydrogen  ;  whilst  the  molecule  of  others  contains  two  atoms 
of  hydrogen  ;  that  is,  two  volumes  of  the  compound  contains 
two  volumes  of  hydrogen  :  in  others,  the  molecule  contains 
three  or  four  atoms  of  hydrogen,  united  in  each  case  to  one 
atom  of  some  other  element.  Thus  one  atom,  or  one  volume 
of  chlorine,  bromine,  iodine,  or  fluorine,  combines  with  one 
atom  or  one  volume  of  hydrogen  to  form  one  molecule,  or  two 
volumes  of  the  several  hydracids,  hydrochloric,  and  hydro- 
bromic,  &c.  :  whilst  one  volume  of  oxygen,  sulphur,  and 
selenium,  on  the  other  hand,  unites  with  two  volumes  of 
hydrogen  to  form  two  volumes  or  one  molecule  of  water  gas, 
or  sulphuretted  hydrogen.  One  volume  of  nitrogen  (or  four 
teen  parts  by  weight),  and  half  a  volume  of  arsenic  and  phos 
phorus  (or,  respectively,  seventy-five  and  thirty-one  parts  by 
weight)  unite,  on  the  other  hand,  with  three  volumes  of  hydro- 


Elementary  Chemistry.  139 

gen  (or  three  parts  by  weight)  to  form  two  volumes  or  one 
molecule  of  ammonia,  phosphuretted  and  arseniuretted  hydro 
gen  ;  whilst  twelve  parts  by  weight  of  carbon  unite  with  four 
volumes  of  hydrogen,  to  form  the  molecule  of  the  typical 
compound,  marsh  gas. 

Hence  we  come  to  distinguish  the  elements  into  groups, 
according  to  their  power  of  combining  with,  or  replacing,  dif 
ferent  quantities  of  hydrogen  :  thus  we  call  chlorine,  bromine, 
iodine,  and  fluorine,  monatomic  elements,  or  monads  ;  oxy 
gen,  Sulphur,  selenium  (and  tellurium),  diatomic  elements,  or 
dyads  j  nitrogen,  phosphorus,  arsenic  (antimony,  bismuth, 
and  boron),  triatomic  elements,  or  triads  j  carbon  (and 
(silicon),  tetratomic  elements,  or  tetrads.  The  class  of 
monads  possess  only  one  combining  power,  or  atomicity^ 
while  the  dyads  possess  two,  the  triads  three,  and  the  tetrads 
four  such  combining  powers.  In  like  manner  the  metallic 
elements  can  be  divided  into  classes  according  to  their 
atomicities,  their  power  of  combining  with  chlorine  and  other 
monads  being  regarded  as  the  measure  of  their  atomicity, 
few  compounds  of  metals  with  hydrogen  being  known. 

Not  only  can  the  elements  thus  be  considered  as  possess 
ing  varying  atomicity,  but  also  those  groups  of  elementary 
atoms,  which  act  collectively  as  elements,  and  to  which  the 
name  of  compound  radicals  is  given.  Thus,  nitric  acid  may, 
as  we  have  seen,  be  considered  as  water,  in  which  one  atom 
of  hydrogen  is  replaced  by  the  monad  radical,  NO2  ;  thus, 

TT    •)  TT        \ 

water  j  [•  O,  nitric  acid,  ^Q  1  O.  Nitric  pentoxide  is  again 
nitric  acid  with  the  second  atom  of  hydrogen  replaced  by  the 
same  radical  ^Q  >  O  =  N2O5.  Sulphuric  acid,  on  the  other 


hand,  may  be  considered  as  built  up  on  the  type  of  two  mole 
cules  of  water,  in  which  two  atoms  of  hydrogen  are  replaced 
by  the  dyad  radical  SO2. 

TT         N 

Water  S2  i  O2.       Sulphuric  Acid      "*  [  O2 
H°> 


140  Elementary  Chemistry. 

Again,  phosphoric  acid  may  be  regarded  as  three  molecules 
of  water,  in  which  three  atoms  of  hydrogen  have  been  replaced 
by  the  triad  radical  PO  ;  thus — 

H3  )  0          PO 
H3f°3         H3 

The  atomicity  of  an  element,  or  of  a  compound  radical, 
may  be  conveniently  expressed  by  placing  the  Roman  nume 
rals  above  the  symbol  for  those  which  are  not  monads,  thus : 

II      III      IV  II  III 

H,  O,  N,  C,  NOa,  SO2,  PO,  &c. 


LESSON  XVII. 

THE  METALLIC  ELEMENTS. 

THE  metals  are  much  more  numerous  than  the  non-metallic 
elements  ;  there  are  fifty  of  the  former,  and  only  fourteen  of 
the  latter :  very  many  metals  are,  however,  found  in  small 
quantities,  and  the  properties  of  these  and  their  compounds 
are  but  little  known,  so  that  in  this  work  we  shall  only  con 
sider  the  most  important  and  commonly  occurring  metals. 

It  has  already  been  stated  that  the  division  of  the  elements 
into  these  two  classes  is  one  of  convenience  only,  and  is  not 
founded  on  any  essential  difference  ;  thus  arsenic  and  anti 
mony  may,  in  some  respects,  be  considered  as  metals,  and  in 
others  as  non-metals. 

All  metals,  with  the  single  exception  of  mercury  (a  liquid), 
are  solid  at  the  ordinary  temperature  ;  they  possess  a  high 
power  of  reflecting  light,  causing  the  bright,  glittering  appear 
ance  known  as  the  metallic  lustre  ;  they  are  better  conductors 
of  heat  and  electricity  than  the  non-rrtetals,  and,  as  a  rule, 
they  have  a  higher  specific  gravity  than  these.  The  metals 


Elementary  Chemistry. 


141 


differ  widely  from  each  other,  both  in  their  physical  and 
chemical  properties,  and  are,  accordingly,  adapted  for  different 
uses ;  those  metals  which  are  lightest  exhibit  the  greatest 
power  of  union  with  oxygen,  whilst  the  heavier  metals  undergo 
oxidation  with  difficulty. 

Physical  Properties  of  the  Metals. 

Specific  Gravity.  —  The  following  table,  giving  the  specific 
gravities  of  the  most  important  metals  (water  at  o°  C.  =  1*00), 
shows  the  great  variation  which  they  exhibit  in  this  respect : 

Table  of  Specific  Gravities. 


Iridium 2r8 

Platinum      .     .     .     .  21*5 

Gold 19-3 

Mercury 13  596 

Thallium       .     .     .     .  11-9 

Palladium     .     .     .     .  ir8 

Lead 11*3 

Silver 10*5 

Bismuth 9*8 

Copper 8*9 

Nickel 8-8 

Cadmium     ....  8'6 

Cobalt 8-5 

Manganese  ....  8'o 


Iron 7-8 

Tin 7'3 

Zinc 7-1 

Antimony 6-7 

Arsenic      .     .     .     .     .  5-9 

Chromium      ....  5-9 

Aluminium     ....  2*56 

Strontium 2*54 

Magnesium    ....  175 

Calcium 1*58 

Rubidium 1*52 

Sodium 0-972 

Potassium 0-865 

Lithium °'593 


Fusibility. — The  melting  points  of  the  metals  differ  even 
more  widely  than  their  densities,  mercury  fusing  at  40°  be 
low  zero,  and  platinum  only  melting  at  the  highest  tempera 
ture  of  the  oxyhydrogen  blowpipe. 


Table  of  Melting  Points. 


Mercury —  40' 

Tin +  235' 


Bismuth 270° 

Cadmium !C 


142  Elementary  Chemistry. 


White  Cast  Iron  .  1,050° 
Gray  ditto  .  1,200° 
Steel.  .  .  1,300°  to  1,400° 
Wrought  Iron  1,500°  to  1,600° 


Lead.     .:....     334° 

Zinc 423° 

Antimony 425° 

Silver 1,000° 

Copper 1,090° 

Some  of  the  metals  can  be  easily  converted  into  vapor,  or 
volatilized  ;  thus  mercury  boils  at  350°,  arsenic  passes  into 
vapor  even  before  it  assumes  the  liquid  form,  whilst  potas 
sium,  sodium,  magnesium,  zinc,  and  cadmium,  can  be  dis 
tilled  at  a  red  heat.  Even  the  more  infusible  of  the  metals, 
such  as  copper  and  gold,  are  not  absolutely  fixed,  but  gi^e 
off  small  quantities  of  vapor  when  strongly  heated  in  a 
furnace. 

The  color  of  most  of  the  metals  is  nearly  uniform,  varying 
from  the  bright  white  of  silver  to  the  bluish-gray  of  lead  ; 
copper  is  the  only  red-colored  metal  known,  whilst  gold, 
strontium,  and  calcium  are  yellow.  In  ductility,  or  the 
power  of  being  drawn  out  into  wire,  and  malleability,  or  the 
power  of  being  hammered  out  into  thin  sheets,  the  metals 
differ  considerably.  Gold  is  the  most  malleable  of  all  the 
metals,  being  capable  of  being  beaten  out  to  the  thickness  of 
the  i-uifoooth  part  of  an  inch  ;  it  is,  likewise,  the  most  ductile 
metal.  Hardness,  brittleness,  and  tenacity,  are  physical 
properties  of  great  importance,  in  which  the  metals  differ 
widely. 

Occurrence  and  Distribiition  of  the  Metals. 

Only  a  few  of  the  metals  occur  in  the  free  or  uncombined 
state  in  nature  ;  in  general  they  are  found  combined  with 
oxygen,  sulphur,  or  some  other  metalloid.  These  metallic 
compounds  exist  most  variously  distributed  throughout  the 
earth's  crust ;  some  are  known  to  occur  in  only  one  or  two 
localities,  and  even  then  only  in  minute  quantity,  whereas 
others  are  found  widely  distributed  in  enormous  masses.  As 
is  seen  by  reference  to  the  table  on  p.  8,  the  metals  alumi 
nium,  iron,  calcium,  magnesium,  and  sodium  occur  in  very  large 


Elementary  Chemistry.  143 

quantities,  forming,  when  united  with  oxygen  and  silicon,  the 
whole  mass  of  granitic  rocks  composing  our  globe  ;  but  it  is 
.  not  from  these  sources  that  the  metals  in  question  can  be  ob 
tained  for  the  purposes  of  the  arts.  For  this  object,  we 
employ  other  combinations,  found  in  smaller  quantity,  from 
which  the  metals  can  be  more  easily  extracted  than  from  the 
silicates,  and  these  compounds  are  termed  the  metallic  ores. 

The  heavy  metals  and  their  ores  generally  occur  inter 
spersed  throughout  the  old  granitic  or  early  sedimentary  rocks 
in  the  form  of  veins  or  lodes,  which  are  cracks,  or  fissures, 
running  through  the  rock  in  a  particular  direction,  and  filled 
up  with  a  metallic  ore.  Other  ores,  such  as  ironstone,  are 
found  amongst  the  more  recent  sedimentary  formations, 
having  been  deposited  in  large  masses,  probably  from  aque 
ous  solution. 

The  consideration  of  the  occurrence  and  distribution  of  the 
various  metallic  ores  belongs  to  the  science  of  geology  ;  the 
study  of  the  modes  of  procuring  the  ores  is  the  province  of 
the  miner  and  engineer  ;  whilst  the  processes  by  means  of 
which  the  metal  itself  is  obtained  from  the  ore,  although  main 
ly  dependent  upon  chemical  principles,  are  generally  classed 
as  belonging  to  the  branch-science  of  metallurgy. 

Classification  of  the  Metals. 

The  metals  can  be  conveniently  grouped  into  classes,  in 
which  the  several  members  possess  certain  properties  and 
general  characters  in  common. 

Class  I.  Metals  of  the  Alkalies.— i,  £0la&sium.  2,  So 
dium.  3,  Caesium.  4,  Rubidium.  5,  Lithium.  (6,  Ammo 
nium.) 

General  Characteristics. — The  metals  of  this  class  are 
monatomic  ;  that  is,  the  atom  of  metal  replaces  one  atom  of 
hydrogen  ;  they  are  soft,  easily  fusible,  volatile  at  higher 
temperatures  ;  they  combine  with  great  force  with  oxygen, 
decompose  water  at  all  temperatures,  and  form  basic  oxides, 
which  are  very  soluble  in  water,  yielding  powerfully  caustic 


144  Elementary  Chemistry. 

and  alkaline  bodies,  from  which  water  cannot  be  expelled  by 
heat.  Their  carbonates  are  soluble  in  water,  and  each  metal 
forms  only  one  chloride.  Ammonium,  NH4,  is  added  to  the 
list  of  alkaline  metals  proper,  from  the  general  similarity  of 
the  ammoniacal  salts  to  those  of  potash  and  soda. 

These  metals  and  their  compounds  are  closely  analogous  in 
their  properties,  and  they  exhibit  a  remarkable  relation  as  re 
gards  their  atomic  weights  ;  thus,  sodium,  which  stands 
between  potassium  and  lithium  in  properties,  has  a  com 
bining  weight,  which  is  the  arithmetic  mean  of  the  other  two, 

39+7  _  23  ;  so,  too,  rubidium,  standing  half-way  between 

caesium  and  potassium,  has  a  mean  atomic  weight,  .  ^      ^9  = 

86. 

Class  II.  .  Metals  of  the  Alkaline  Earths.— i,  Calcium. 
2,  Strontium.  3,  Barium. 

General  Characteristics. — The  metals  of  this  class  are  dia 
tomic  ;  that  is,  the  atom  replaces  two  atoms  of  hydrogen  ;  the 
metals  cannot  be  reduced  by  hydrogen  or  carbon  alone,  they 
decompose  water  at  all  temperatures,  producing  oxides,  which 
combine  with  water  to  form  hydrates,  from  some  of  which  the 
water  can  be  driven  off  by  heat.  Their  carbonates  are  inso 
luble  in  water,  but  soluble  in  water  containing  carbonic  acid 
in  solution. 

Class  III.  Metals  of  the  Earths. — i,  Aluminium.  2, 
Glucinium.  3,  Zirconium.  4,  Thorium.  5,  Yttrium.  6, 
Erbium.  7,  Cerium.  8,  Lanthanum.  9,  Didymium. 

With  the  exception  of  aluminium,  these  metals  are  hardly 
known  in  the  free  state,  as  their  compounds  occur  so  rarely 
that  they  are  not  employed  for  any  useful  purpose,  and  their 
properties  cannot  be  considered  in  an  elementary  work.  The 
oxides  of  this  group  are  insoluble  in  water  ;  and  they  cannot 
be  reduced  to  the  metallic  state  by  hydrogen  or  carbon. 
Aluminium  is  tetratomic,  one  atom  replacing  four  atoms  of 
hydrogen. 

Class  IV.       Zinc   Class. — i,    Magnesium.      2,  Zinc.      3, 


Elementary  Chemistry.  145 

Cadmium.  These  metals  are  diatomic  ;  they  are  all  volatile 
~at  Tiigh  temperatures,  and  burn  when  heated  in  the  air :  they 
decompose  water  at  a  high  temperature,  or  in  presence  of  an 
acid,  and  form  only  one  oxide  and  one  chloride. 

Class  V.  Iron  Class. — i,  Manganese.  2,  Iron.  3,  Co 
balt.  4,  Nickel.  5,  Chromium.  6,  Uranium.  7,  Indium. 
These  are  diatomic,  and  equivalent  to  two  atoms  of  hydro 
gen  ;  they  are  not  volatile  at  the  temperature  of  our  fur 
naces  ;  they  decompose  water  like  the  preceding  class,  and 
they  form  several  oxides,  chlorides,  and  sulphides. 

Class  VI.  Tin  Class. — I,  Tin.  2,  Titanium.  3,  Niobium. 
4,  Tantalum.  Tin  is  the  only  one  of  this  class  employed  in 
the  arts.  These  metals  decompose  water  at  high  temperatures 
and  in  presence  of  alkalies  ;  they  form  dioxides  and  volatile 
tetrachlorides,  and  are  hence  tetratomic. 

Class  VII.  Tungsten  Class. — i,  Molybdenum.  2,  Vana 
dium.  3,  Tungsten.  These  metals  are  all  of  rare  occurrence  ; 
they  decompose  water  at  a  high  temperature,  and  form  tri- 
oxides  and  volatile  hexachlorides. 

Class  VIII.  Arsenic  Class. — i,  Arsenic.  2,  Antimony. 
3,  Bismuth.  The  metals  of  this  class  are  triatomic,  they  form 
the  junction  between  the  metals  and  metalloids,  and  they 
closely  resemble  phosphorus  in  their  properties. 

Class  IX.  Lead  Class. —  r,  Lead.  2,  Thallium:  heavy 
metals,  allied  in  their  general  properties  to  the  two  first  classes. 
Lead  is  diatomic,  but  thallium  is  monatomic. 

Class  X.  Silver  Class. — i,  Copper.  2,  Mercury.  3,  Silver. 
These  metals  do  not  decompose  water  under  any  circum 
stances  ;  they  are  oxidized  by  nitric  and  strong  sulphuric 
acids ;  copper  and  mercury  form  two  basic  oxides  which, 
except  in  the  case  of  copper,  are  decomposed  by  heat  alone. 
Copper  and  mercury  are  diatomic  ;  silver  is  monatomic. 

Class  XI.  Gold  class. — i,  Gold.  2,  Platinum.  3,  Palla 
dium.  4,  Rhodium.  5,  Ruthenium.  6,  Iridium.  7,  Osmium. 
These  metals  are  not  acted  upon  by  nitric  acid,  but  only  by 
chlorine  or  aqua  regia,  and  the  oxides  are  reduced  by  heat 
alone  ;  and  they  with  silver  and  mercury  constitute  the  noble 

7 


146  Elementary  Chemistry. 

metals.     Gold  is  triatomic,  and  the  other  members  of  this 
class  are  tetratomic. 


Chemical  Properties  of  the  Metals. 

The  metals  combine  (i)  with  each  other  to  form  alloys  ;  (2) 
with  the  metalloids  to  form  oxides,  sulphides,  chlorides,  &c. 
In  the  alloys  the  metallic  appearance  and  properties  are  pre 
served,  whereas  in  the  compounds  with  the  metalloids  the 
physical  properties  of  the  metals  as  a  rule  disappear. 

Alloys.  The  compounds  formed  by  the  metals  amongst 
themselves  are  not  so  stable  as  those  which  are  formed  by 
union  with  a  metalloid  ;  nevertheless  the  alloys  are  largely  used 
in  the  arts,  as  they  possess  many  valuable  properties  not 
exhibited  by  the  metals  separately.  Thus  gold  and  silver  are 
too  soft  to  be  used  alone  as  a  medium  of  currency,  but  the 
addition  of  7-5  per  cent,  of  copper  gives  an  alloy  of  the  requi 
site  hardness  ;  then  copper  is  too  soft  and  tough  to  be  wrought 
in  the  lathe,  but  when  alloyed  with  half  its  weight  of  zinc  it 
forms  a  hard  and  most  useful  substance  known  as  brass. 
Gun-metal,  or  bronze,  is  a  hard  and  tenacious  alloy  of  90  parts 
of  copper  and  10  of  tin.  Bell-metal,  a  still  harder  alloy, 
contains  the  same  metals  in  the  proportion  of  80  of  the  former 
to  20  of  the  latter,  whilst  an  alloy  of  33  parts  of  tin  to  67  of 
copper  possesses  a  white  color,  takes  a  high  polish,  and  is 
known  as  speculum-metal,  and  employed  for  the  reflectors  of 
telescopes.  For  making  printing  type  a  peculiar  alloy  is 
employed,  containing  80  parts  of  lead  to  20  of  antimony  ;  this 
possesses  many  properties  necessary  for  type  metals,  which 
are  found  to  belong  to  no  single  metal  or  other  alloy. 

The  chemical  composition  of  the  alloys  is  not  so  definite  or 
so  well  marked  as  that  of  the  other  metallic  compounds,  but 
they  may  frequently  be  obtained  in  crystals  in  which  the  con 
stituents  are  contained  in  atomic  proportions,  The  melting 
point  of  an  alloy  is  often  much  lower  than  the  melting  points 
of  its  constituent  metals.  Thus  lead  melts  at  334°,  bismuth 


Elementary  Chemistry.  147 

at  270°,  tin  at  235°,  and  cadmium  at  315° ;  whereas  an  alloy 
of  2  parts  bismuth,  I  of  tin,  and  I  of  lead,  melts  at  95°  to 
98°  C,  and  one  containing  8  of  lead,  15  bismuth,  4  of  tin,  and 
3  of  cadmium,  softens  at  as  low  a  temperature  as  60°,  and  is 
perfectly  fluid  at  65°  C.  The  alloys  of  metals  with  mercury 
are  termed  Amalgams. 


Compounds  of  the  Metals  with  Metalloids. 

1.  Metallic  Oxides.     Oxygen  acts  very  differently  on  the 
different  metals.     Some  metals,  such  as  zinc,  magnesium,  and 
calcium  take  fire  when  heated,  and  burn  with  the  evolution 
of  intense  light  ;  whilst  others,  such  as  gold  and  silver,  do 
not  combine  directly  with  oxygen,  and  are  only  obtained  in 
combination  with  it  by  indirect  means  and  with  difficulty. 

The  oxides  differ  widely  in  properties  and  composition  ; 
they  may,  however,  all  be  represented  as  water  in  which  the 
hydrogen  has  been  replaced  by  metal.  Thus  the  monoxides 
may  be  considered  to  be  water  in  which  either  each  atom  of 
hydrogen  is  replaced  by  a  monad,  as  K2O,  Ag2O,  or  the  two 
atoms  of  hydrogen  are  replaced  by  a  dyad,  as  Ba  O,  Zn  O  ; 
whilst  the  higher  oxides  are  regarded  as  two  or  more  mo 
lecules  of  water,  in  which  the  hydrogen  is  in  like  manner 
replaced  by  its  equivalent  of  metal.  The  most  important  of 
these  higher  oxides  are  the  sesquioxides,  such  as  alumina, 
A12  O3,  and  ferric  oxide,  Fe2  O3 ;  the  dioxides,  such  as  black 
oxide  of  manganese,  Mn  Oa ;  the  trioxides,  as  chromium  tri- 
oxide,  CrO3. 

2.  Metallic  Sulphides.     Metals  combine  directly  with  sul 
phur  to  form  sulphides,  and  these  occur  frequently  in  nature, 
forming  many  of  the  metallic  ores.     These  compounds  re 
semble  in  composition  the  corresponding  oxides,  and  may  be 
represented  as   sulphuretted    hydrogen,  H2S,  in  which   the 
hydrogen  is  replaced  by  its  equivalent  of  metal.     The  sul 
phides  of  the  first  and  second  class  of  metals  are  soluble  in 
water ;  those  of  the  remaining  almost  all  insoluble  in  water, 


148  Elementary  Chemistry. 

but  some  of  them  soluble,  and  others  insoluble,  in  acids  and 
alkalies.  In  the  laboratory  this  difference  in  the  solubility 
of  the  sulphides  is  employed  as  a  means  of  separating  the 
different  metals  in  the  processes  of  chemical  analysis. 

3.  Metallic  Chlorides.     The  metals  unite  directly  with  chlo 
rine  to  form  an  important  class  of  compounds,  which  may 
be  considered   as   one   or   more    molecules    of  hydrochloric 
acid,  in  which  the  hydrogen  is  replaced  by  its  equivalent  of 
metal ;  thus  K  Cl  is  the  chloride  of  a  monad  ;  Ba  C12  that  of 
a  dyad,  and  this  may  be  considered  as  two  molecules  of  hydro 
chloric  acid,  in  which  two  atoms  of  hydrogen  are  replaced  by 
the  dyad  barium  ;  whereas  antimony  trichloride,  SbCU,  may 
be  represented  as   three  molecules  of  hydrochloric  acid,   in 
which  the  three  atoms  of  hydrogen  are  replaced  by  one  atom 
of  triatomic  antimony. 

4.  Metals  unite  with  bromine,  iodine,  fluorine,  and  cyanogen 
to  form  bromides,  iodides,  fluorides,  and  cyanides,  all  of  which 
bear  a  strong  resemblance  to  the  corresponding  chlorides, 
and  may  be  considered  to  possess  an  analogous  constitution. 

5.  Metals   also    unite    with    nitrogen,    phosphorus,    boron, 
silicon,  carbon,  and  hydrogen  ;  but  the  compounds  thus  formed 
are  in  general  of  slight  importance. 

6.  Metallic  Salts. — The  replacement  of  the  hydrogen  in 
acids  (the  hydrogen  salt),  by  its  equivalent  of  metal,  gives  rise 
to  the  formation  of  a  very  large  class  of  bodies  to  which  the 
name  of  metallic  salts  has  been  given  ;    thus,  if  we  replace 
both  atoms    of  hydrogen    in    hydric   sulphate,  Ha    SO4,    by 
potassium,  we  get  potassium-sulphate,  K2  SO4 ;  if  only  one 
is  replaced,  we  have  hydric-potassium  sulphate,  KH  SO4 ;  if  we 
replace  both   the  atoms   of  hydrogen  with  a  dyad,  we  have 
Ba  SO4,  or  Zn  SO4.     The  same  holds  goqd  for  all  the  other 
acids  ;  thus,  H3  PO4  (trihydric  phosphate)  yields  Ag3  PO4 
(trisilver  phosphate) ;    H   NO3  yields  K  NO8,  or  Ba  N2  Oe. 
The  metals  forming  sesquioxides  also  give  rise  to  salts  which 
may  be  considered  as  being  composed  of  several  molecules 
of  the  acid  with   the  hydrogen  replaced  by  the  metal ;  thus 
aluminium    sulphate  is  three  molecules  of  hydric  sulphate. 


Elementary  Chemistry.  149 

3  (Ha  SO4),  in  which  the  6  of  hydrogen  are  replaced  by  2  atoms 
of  aluminium  ;  thus,  A12  3  SO4.  The  constitution  of  the  other 
classes  of  salts  will  be  best  understood  from  the  special 
descriptions.  Many  of  the  metallic  salts  when  crystallized 
contain  a  definite  number  of  atoms  of  water,  and  this  is  termed 
'water  of  crystallization. 

(-v  /  rjsps 

LESSON   XVIIL 

(     V  /    r 

Crystallography. 


Most  chemical  substances,  when  they  pass  from  the  liquid 
or  gaseous  into  the  solid  state,  assume  some  definite  geome 
tric  form,  or  are  said  to  crystallize.  Crystals  are  produced 
when  a  substance,  such  as  nitre,  is  dissolved  in  water  and 
the  solution  allowed  gradually  to  evaporate  ;  or  when  a  body, 
such  as  sulphur,  is  melted  and  allowed  to  solidify  by  cooling  ; 
or  when  a  volatile  substance,  such  as  iodine  or  arsenious 
oxide,  is  vaporized  and  the  vapor  condensed  on  a  cool  surface. 
Many  naturally  occurring  minerals  exhibit  very  perfect  crys 
talline  forms  ;  we  are  ignorant  of  the  mode  in  which  such 
crystals  are  in  most  cases  produced,  but  we  know  that  the 
process  of  their  formation  has  been  a  very  slow  one,  and  we 
find  that,  in  general,  a  crystal  is  larger  and  more  perfect  the 
more  gradually  it  has  been  formed.  Crystalline  bodies  exhibit, 
in  addition  to  their  regular  form,  a  peculiar  power  of  splitting 
in  certain  directions  more"  readily  than  in  others,  called  cleav 
age;  as  well  as  in  many  cases  the  property  of  allowing  the 
rays  of  light  and  heat  to  pass  more  readily  in  one  direction 
than  another,  giving  rise  to  the  well-known  phenomena  of 
double  refraction. 

Inorganic  bodies  which  do  not  exhibit  these  peculiarities,  or 
assume  crystalline  structure,  are  said  to  be  amorphous ;  but 
certain  highly  complicated  structures  found  in  the  vegetable 


150  Elementary  Chemistry. 

and  animal  world  exhibit  a  structure  which,  although  it  is 
non-crystalline,  is  not  devoid  of  arrangement,  and  to  which 
the  name  organized  or  cellular  structure  has  been  given. 
As  a  rule,  every  particular  substance  possesses  a  definite 
form  in  which  it  always  crystallizes,  and  by  which  it  can  be 
distinguished ;  when  a  crystal  is  formed,  from  aqueous  solu 
tion,  for  example,  the  smallest  visible  particle  possesses  the 
complete  form  of  the  largest  crystal,  and  simply  increases  in 
size  without  undergoing  any  change  of  form. 

It  has  been  found  possible  to  arrange  the  many  thousand 
different  known  crystals  in  six  systems,  to  each  of  which 
belongs  a  number  of  forms  having  some  property  in  common. 
In  order  to  classify  these  different  crystals,  the  existence  of 
certain  lines  within  the  crystal  called  axes  is  supposed,  round 
which  the  form  can  be  symmetrically  built  up.  These  axes 
are  assumed  to  intersect  in  the  centre  of  the  crystal,  and  pass 
through  from  one  side  to  the  other. 

1st,  or  Regular  System. — Three  axes,  all  equal  and  at  right 
angles.  The  simple  forms  of  this  system  are  (i)  the  cube 

ig-  37) ;  (2)  the  regular  octohedron  (Fig.  38) ;  (3)  the  rhom- 


FIG.  37.  •  FIG.  38. 

bic  dodecahedron  (Fig.  39) ;  and  (4)  the  regular  tetrahedron 
(Fig.  40).  The  following  are  a  few  of  the  substances  crystal 
lizing  in  this  system — alum,  common  salt,  diamond,  fluor-spar, 
iron  pyrites,  and  garnet. 


Elementary  Chemistry.  151 


2^,  or  QZZBB^  System. — Three  axes,  all  at  right  angles, 
one  shorter  or  longer  than  the  other  two.  The  simple  forms 
of  this  system  are  the  first  and  second  right  square  prisms 


FIG.  39.  FIG.  40. 

(Fig.  41  a  and  b\  and  the  first  and  second  right  square  octo- 
hedra  (Fig.  42  a  and  b}.     In  the  first  square  prism  the  axes 


FIG.  41  a.  FIG.  41  b. 

terminate  in  the  centre  of  each  of  the  sides,  and  in  the  second 
the  axes  terminate  at  the  intersection  of  the  sides,  and  this  is 
reversed  with  regard  to  the  octohedra.  Some  of  the  common 
substances  which  crystallize  in  this  system  are — yellow  prus- 
siate  of  potash,  zircon,  and  stannic  oxide. 

The  34  or  Hexagonal  System. — Four   axes,  three    equal 


152 


Elementary  Chemistry. 


and  in  one  plane,  making  angles  of  60°,  and  one  longer  or 
shorter,  at  right  angles  to  the  plane  of  the  other  three.     The 


FIG.  42  «. 


FIG.  42  b. 


regular  six-sided  prism  (Fig  43),  the  regular  six-sided  pyramid 
(Fig.  44),  and  the  rhombohedron  (Fig  45),  are  the  common 


FIG.  43- 


FIG.  44- 


forms  of  this  system.     Quartz,   calc-spar,  beryl,  corundum, 
graphite,  &c.,  crystallize  in  the  hexagonal  system. 

^th  or  Rhombic  System. — Three  axes,  all  unequal,  and  all 
at  right  angles.  The  chief  forms  of  the  crystals  in  this  system 
are  the  right  octohedron  with  rhombic  base  (Figs.  46  and  47), 
and  the  right  rhombic  prism  (Fig.  48).  In  this  system  the 


Elementary  Chemistry. 


153 


following  substances  are  found — nitre,  barium  sulphate,  arra- 
gonite,  topaz,  and  native  sulphur. 

$th  or  Monoclinic  System. — Three  axes,  all  unequal,  two 


FIG.  45. 


FIG.  46. 


cut  one  another  obliquely,  and  one  is  at  right  angles  to  the 
plane  of  the  other  two.  The  oblique  rhombic  octohedron 
(Fig.  49)  belongs  to  this  system.  Many  substances  crystal- 


FIG.  47. 


FIG.  48. 


lize  in  this  system  ;  amongst  the  most  common  are — sulphur 
deposited  from  fusion,  sodium  carbonate  and  phosphate,  fer 
rous  sulphate,  and  borax. 

6M,  or  Triclinic  System. — Three  axes,  all  unequal,  and  all 
oblique.  The  doubly-oblique  octohedron,  and  the  doubly- 
oblique  prism  (Fig.  50),  are  the  leading  forms  in  this  system. 

7* 


154 


Elementary  Chemistry, 


Copper  sulphate,  boracic  acid,  the  mineral  albite,  and  a  few 
other  substances  are  found  to  crystallize  in  this  system,  the 
forms  of  which  are  in  general  very  complicated.  The  crys 
talline  form  of  copper  sulphate  is  shown  in  Fig.  51. 


FIG.  49. 

Under  one  or  other  of  these  six  divisions  all  the  known 
forms  of  crystals  can  be  classed.  In  every  distinct  crystal 
belonging  to  any  one  of  these  systems,  in  which  the  axes  are 
not  all  equal,  or  all  at  right  angles,  certain  relations  exist  be- 


FIG.  50. 

tween  the  lengths  of  the  axes,  and  these  have  certain  mutual 
inclinations  to  one  another.  These  relations  and  inclinations 
vary  with  different  substances,  but  are  constant  for  the  same  ; 
so  that  different  bodies  all  crystallizing  in  the  same  system, 


Elementary  Chemistry.  155 

as  a  rule,  have  different  relations  between  the  lengths  of  the 
axes,  and  these  generally  have  different  inclinations  to  one 
another. 

Certain  substances  exhibiting  a  similarity  in  their  chemical 

/  >.  A» 

** 


FIG.  51. 

constitution  are  found  to  crystallize  in  the  same  forms  :  these 
are  said  to  be  isomorphous  ;  whilst,  when  the  same  body 
occurs  crystallized  in  two  different  systems,  it  is  said  to  be 
dimorphous.  Examples  of  these  peculiar  relations  between 
chemical  composition  and  crystalline  form  will  be  given  later 
on. 


LESSON  XIX. 

CLASS  I.  METALS  OF  THE  ALKALIES. — i,  POTASSIUM. 
2,  SODIUM.  3,  CESIUM.  4,  RUBIDIUM.  5,  LITHIUM.  (6, 
AMMONIUM.) 

POTASSIUM.  Symbol  K.  Combining  Weight  39' I.  Specific 
Gravity  0*865. 

The  metal  potassium  was  discovered  in  the  year  1807,  by 
Sir  Humphrey  Davy,  who  decomposed  the  alkali  potash  into 
the  metal,  hydrogen,  and  oxygen,  by  means  of  a  powerful 
galvanic  current.  Before  this  time  the  alkalies  and  alkaline 


156  Elementary  Chemistry. 

earths  were  supposed  to  be  elementary  bodies.  The  metal  is 
now  prepared  by  heating  together  potash  and  carbon  to  a 
high  temperature  in  an  iron  retort.  The  carbon,. at  the  high 
temperature,  is  able  to  take  the  oxygen  from  the  potash,  form 
ing  carbonic  oxide,  which  escapes  as  a  gas,  whilst  the  metal 
potassium,  which  is  volatile  at  a  red  heat,  distils  over.  The 
preparation  of  this  metal  is  attended  with  many  difficulties, 
and  requires  special  precautions,  as  the  vapor  of  potassium 
not  only  takes  fire  when  brought  in  contact  with  the  air,  but 
decomposes  water,  combining  with  the  oxygen  and  liberating 
hydrogen  ;  hence  the  metallic  vapor  must  be  cooled  by  rock 
oil  or  naphtha,  which  contains  no  oxygen.  The  metal  thus 
prepared  must  be  distilled  a  second  time,  in  order  to  purify 
it  and  free  it  from  a  black,  explosive  compound,  which  inva 
riably  forms  in  the  original  preparation,  and  has  caused  sev 
eral  fatal  accidents. 

Potassium,  thus  prepared,  is  a  bright,  silver-white  metal, 
which  can  be  easily  cut  with  a  knife  at  the  ordinary  atmo 
spheric  temperature  ;  it  is  brittle  at  o°,  and  melts  at  620>5, 
and  does  not  become  pasty  before  melting;  when  heated  to  a 
temperature  below  red  heat,  potassium  sublimes,  yielding  a 
fine  green-colored  vapor.  This  metal  rapidly  absorbs  oxygen 
when  exposed  to  the  air,  and  gradually  becomes  converted 
into  a  white  oxide.  Thrown  into  water,  one  atom  of  potas 
sium  displaces  one  of  hydrogen  from  the  water,  forming 
potassium  hydroxide,  KHO  ;  this  takes  place  with  such  force 
that  the  heat  developed  is  sufficient  to  ignite  the  hydrogen 
thus  set  free,  and  the  flame  becomes  tinged  with  the  peculiar 
purple  tint  characteristic  of  the  potassium  compounds,  whilst 
the  water  attains  an  alkaline  reaction  from  the  potash  which 
is  formed.  Potassium  combines  also  with  chlorine  and  sul 
phur,  and  many  other  metalloids,  evolving,  when  heated  with 
these  substances,  heat  and  light. 

Sources  of  the  Potassium  Compounds. — The  original  source 
of  potassium  compounds  is  in  the  felspar  of  the  granitic  rocks, 
of  which  the  earth  is  composed,  as  these  contain  from  two  to 
three  per  cent,  of  this  metal.  Up  to  the  present  time,  this 


Elementary  Chemistry,  157 

source  has  not  been  available  for  the  manufacture  of  the 
potassium  salts,  as  no  cheap  and  easy  mode  has  yet  been 
made  available  for  separating  the  potash  from  the  silicic  acid, 
with  which  it  is  combined  in  felspar.  Plants,  however,  are 
able  slowly  to  separate  out  and  assimilate  the  potash  from 
these  rocks  and  soils  ;  so  that,  by  burning  the  plant  and  ex 
tracting  the  ashes  with  water,  soluble  potash-salt  is  obtained. 
This  is  the  crude  potassium  carbonate,  called,  when  purified 
by  recrystallization,  pearl-ash,  and  it  is  from  this  substance 
that  a  large  number  of  the  potassium  compounds  are  obtained. 
Some  of  the  other  potassium  salts,  such  as  the  nitrate  and 
chloride,  are  found  in  large  quantities  in  various  localities  as 
deposits  on  the  surface,  or  in  the  interior,  of  the  earth. 
Potassium  chloride  occurs  in  beds  together  with  rock  salt, 
in  Stassfurt  in  Germany.  Another  inexhaustible  source  of 
potassium  compounds,  which,  however,  has  only  just  begun 
to  be  utilized,  is  sea-water  :  a  plan  has  lately  been  proposed 
by  which  those  compounds  can  be  obtained  from  the  sea. 

Potassium  Oxides. — Potassium  combines  with  oxygen  in 
three  proportions,  forming  three  well-defined  oxides  of  the 
formulae — 

(1)  Potassium  monoxide K2O 

(2)  Potassium  dioxide K2O2 

(3)  Potassium  tetroxide K2O4 

These  oxides  are  unimportant  bodies  ;  but  potash,  the 
compound  of  the  first  with  water,  is  a  substance  of  great 
importance. 

Potassium  monoxide,  K.2O,  is  obtained  by  allowing  thin 
pieces  of  the  metal  to  oxidize  in  dry  air  ;  it  is  a  grayish-white, 
brittle  substance,  which  melts  a  little  above  red  heat,  and 
volatilizes  only  at  a  very  high  temperature.  This  oxide  com 
bines  with  water  with  evolution  of  great  heat,  producing 
potassium  hydroxide,  or  potash,  from  which  water  cannot 
again  be  separated  by  heat.  The  reaction  may  be  repre 
sented  as  an  exchange  of  hydrogen  for  potassium,  thus  : 

K3O  +  H,O  =  2(KHO). 


158  Elementary  Otemistry. 

Potassium  Hydroxide,  or  Caustic  Potash,  HKO,  is  ob 
tained  as  above,  or  more  conveniently  prepared  by  boiling 
one  part  of  potassium  carbonate  with  twelve  parts  of  water, 
and  adding  slacked  lime  prepared  from  two-thirds  part  of 
quick  lime.  In  this  reaction  calcium  carbonate  is  formed, 
which  falls  to  the  bottom  as  a  heavy  powder,  caustic  potash 
remaining  in  solution.  The  clear  liquid,  which  should  not 
effervesce  on  addition  of  an  acid,  is  evaporated  in  a  silver 
basin  to  dryness,  fused  by  exposure  to  a  stronger  heat,  and 
cast  into  sticks  in  a  metallic  mould.  Thus  prepared,  caustic 
potash  is  a  white  substance,  soluble  in  half  its  weight  of 
water,  acting  as  a  powerful  cautery,  destroying  the  skin.  It 
is  largely  used  in  the  arts  and  manufactures,  and  is  employed 
in  the  laboratory  for  various  purposes. 

Potassium  Carbonate.  Symbol  K2COs.  This  salt  re 
ceives  the  commercial  name  of  potashes,  or  pearl-ashes,  and 
is  imported  in  large  quantities  from  Russia  and  America.  The 
crude  substance  is  prepared  by  boiling  out  the  ashes  of 
plants  with  water,  and  evaporating  the  solution  to  dryness  ;  a 
pure  salt  may  be  afterwards  obtained  by  separating  the  im 
purities  by  crystallization.  The  leaves  and  small  twigs  of 
plants  contain  more  potash  than  the  stems  and  large 
branches.  Potassium  carbonate  can  be  obtained  perfectly 
pure  by  heating  pure  potassium  tartrate  to  redness,  and 
separating  the  carbonate  formed  by  dissolving  in  water.  This 
salt  absorbs  water  from  the  air,  or  is  deliquescent,  and  is, 
therefore,  very  soluble  in  water  ;  it  also  turns  red  litmus  blue, 
or  possesses  a  strongly  alkaline  reaction. 

Hydric  Potassium  Carbonate,  HKCO3.  This  substance  is 
formed  when  a  current  of  carbonic  acid  gas,  CO2,  is  passed 
through  a  strong  solution  of  the  preceding  salt.  It  may  be 
considered  as  dibasic  carbonic  acid,  HaCOa,  in  which  one  atom 
of  hydrogen  is  replaced  by  one  of  potassium.  It  is  a  white 
salt,  not  so  soluble  as  potassium  carbonate  ;  the  solution  is 
nearly  neutral  to  test  paper. 

Potassium  Nitrate,  Nitre,  or  Saltpetre,  KNO3.  This  im 
portant  salt  occurs  as  an  efflorescence  on  the  soil  of  several 


Elementary  Chemistry.  159 

dry  tropical  countries,  especially  that  of  India.  It  may  be 
artificially  prepared  by  the  process  of  nitrification,  in  which 
animal  matter  (containing  nitrogen)  is  exposed  in  heaps, 
mixed  together  with  wood-ashes  and  lime,  to  the  action  of  the 
air  ;  the  organic  matter  gradually  undergoes  oxidation,  nitric 
acid  being  formed,  and  this  unites,  first  with  the  lime  and 
then  with  the  potash,  to  form  nitre.  The  salt  is  obtained 
from  both  of  these  sources  by  boiling  out  the  soil  or  deposit 
with  water,  and  allowing  the  nitre  to  crystallize  out.  Nitre 
crystallizes  in  rhombic  prisms  ;  it  dissolves  in  seven  parts  of 
water,  at  15°,  and  in  its  own  weight  of  hot  water.  It  contains 
nearly  half  its  weight  of  oxygen,  with  which  it  parts  on  heat 
ing  with  carbon  or  other  combustible  matter.  For  this  rea 
son,  nitre  is  largely  used  in  the  manufacture  of  gunpowder 
and  fireworks.  Gunpowder  consists  of  an  intimate  mixture 
of  nitre,  charcoal,  and  sulphur.  The  general  decomposition 
which  occurs  when  gunpowder  is  fired  may  be  expressed  by 
saying  that  the  oxygen  of  the  nitre  combines  with  the  char 
coal,  forming  carbonic  acid  and  carbonic  oxide,  whilst  the 
nitrogen  is  liberated,  and  the  sulphur  combines  with  the 
potassium.  Hence  gunpowder  can  burn  under  water  or  in  a 
closed  space,  as  it  contains  the  oxygen  needed  for  the  com 
bustion  in  itself,  and  the  great  explosive  power  of  the  sub 
stance  is  due  to  the  violent  evolution  of  large  quantities  of 
gas,  and  a  rapid  rise  of  temperature  causing  an  increase  of 
bulk  sudden  and  great  enough  to  produce  what  is  termed  an 
explosion.  It  has  been  found  by  practice  that  the  best  gun 
powder  is  that  which  contains  nearly  two  atoms  of  nitre,  one 
of  sulphur,  and  three  of  carbon  ;  but  the  decomposition  which 
actually  occurs  in  the  explosion  is  a  more  complicated  one 
than  has  been  expressed  above,  and  cannot  be  represent 
ed  in  an  equation.  The  following  table  (see  p.  160)  gives 
the  composition  of  musketry  powder,  as  manufactured  by 
different  nations. 

Potassium  combines  with  sulphur  to  form  several  com 
pounds,  of  which  the  best  known  are  K2S,  K2S2,  K2S3,  and 
K3S6.  They  are  soluble  substances,  which  evolve  sulphu- 


i6o 


Elementary  Chemistry. 


retted  hydrogen  when  heated  with  an  acid,  and  are  not  used 
in  the  arts. 


1 

Nitre   

English 
and 
Austrian. 

Prussian. 

Chinese. 

French. 

75 

75 

757 

75-0 

Charcoal  .... 

'5 

13-5 

14-4 

I2'5 

Sulphur    .... 

10 

ii'S 

9-9 

I2'5 

100 

I  OO'O 

I  OO'O 

I  OO'O 

The  remaining  compounds  of  potassium  of  interest  and  im 
portance  are — potassium  chloride,  KC1,  occurring  in  sea-water 
and  also  in  certain  deposits  ;  potassium  iodide,  KI,  men 
tioned  under  the  head  of  Iodine  ;  potassium  bromide,  K  Br 
(see  ante,  p.  95) ;  potassium  chlorate,  KC1  O3,  the  prepara 
tion  of  which  was  described  under  Hydric  Chlorate,  (p.  93)  ; 
potassium  sulphate,  K2SO4,  one  of  the  most  insoluble  of  the 
salts  of  this  metal  ;  and  hydric  potassium  sulphate,  HKSO4. 

General  Characteristics  of  the  Potassium  Compounds. 

All  the  potassium  compounds  impart  a  violet  color  to  the 
flame,  and  the  spectrum  of  this  flame  (see  p.  220,  spectrum 
analysis)  is  distinguished  by  the  presence  of  two  bright  lines, 
one  in  the  red,  and  another  in  the  violet.  Almost  all  the 
potassium  salts  are  soluble  in  water  ;  the  three  which  are 
least  soluble  are — (i)  potassium  perchlorate  ;  (2)  hydric- 
potassium  tartrate,  which  is  precipitated  in  the  form  of  a 
white  crystalline  powder,  when  a  solution  of  a  potassium  salt 
is  mixed  with  an  excess  of  tartaric  acid ;  and  (3)  potassium- 
platinum  chloride,  2(KC1)  +  Pt  C14,  which  precipitates  in  small 
yellow  cubical  crystals,  when  platinum  chloride  solution  is 
added  to  a  soluble  potassium  salt.  These  reactions  serve  to 
distinguish  the  potassium  salts. 


Elementary  Chemistry.  161 

2.  SODIUM.  Symbol  Na  (natrium).  Combining  Weight 
23.  Specific  Gravity  0*97. 

This  metal  was  discovered  by  Sir  H.  Davy  immediately 
after  the  isolation  of  potassium,  by  the  decomposition  of  soda 
with  the  galvanic  current.  It  can  be  procured  more  easily 
than  potassium  by  reducing  the  carbonate  in  presence  of 
carbon,  and  is  now  manufactured  in  large  quantities  for 
the  preparation  of  other  metals,  especially  magnesium  and 
aluminium.  The  apparatus  employed  for  the  preparation  of 
this  metal  is  the  same  as  that  used  for  potassium  ;  the  metal 
distils  over  when  condensed,  and  drops  into  rock  oil.  So 
dium  is  a  silver-white  metal,  soft  at  ordinary  temperatures, 
and  melting  at  95°'6  ;  it  volatilizes  below  a  red  heat,  yielding 
a  colorless  vapor.  When  thrown  upon  water  it  floats,  and 
rapidly  decomposes  the  water  with  disengagement  of  hydro 
gen,  soda  being  formed.  If  the  water  be  hot  or  be  thickened 
with  starch,  the  globule  of  metal  becomes  so  much  heated  as 
to  enable  the  hydrogen  to  take  fire.  The  compounds  of 
sodium  are  very  widely  diffused,  being  contained  in  every 
speck  of  dust  (see  spectrum  analysis,  p.  221) ;  they  exist  in 
enormous  quantities  in  the  primitive  granitic  rocks  (see  p.  8), 
but  they  are  most  readily  obtained  from  sea-water,  which  con 
tains  nearly  three  per  cent,  of  sodium  chloride  (common  or 
sea-salt),  or  from  the  large  deposits  of  this  substance  which 
occur  in  Cheshire,  Galicia,  &c.  Sodium  carbonate  was 
formerly  obtained  from  the  ashes  of  sea-plants  or  kelp, 
as  potassium  carbonate  is  still  prepared  from  the  ashes  of 
land  plants  ;  but  at  present  the  sodium  carbonate  is  alto 
gether  manufactured,  on  an  enormously  large  scale,  from  sea 
salt. 

Sodium  Oxides.  There  are  two  compounds  of  sodium  and 
oxygen  known.  Sodium  oxide,  Na2  O  ;  and  sodium  dioxide, 
Na-j  O2 — Sodium  Oxide,  Na2  O,  is  formed  when  sodium  is 
oxidized  in  dry  air  or  oxygen  at  a  low  temperature,  a  white 
powder  being  formed  ;  this  takes  up  moisture  with  great  avidity, 
forming  H  Na  O,  sodium  hydroxide,  or  soda,  from  which  the 
water  cannot  again  be  separated  by  heat  alone,  but  which  can 


1 62  Elementary  Chemistry. 

again  be  converted  into  the  oxide  by  heating  with  sodium ; 
thus,  H  NaO  +  Na  =  Na3O  +  H. 

Sodium  Dioxide,  Na2  O2,  is  a  yellowish- white  powder, 
which  is  formed  when  sodium  is  heated  in  oxygen  to  200°  C.  ; 
it  is  soluble  in  water,  but  the  solution  readily  decomposes, 
giving  off  oxygen  and  leaving  sodium  hydrate.  Sodium 
dioxide  is  not  used  in  the  arts. 

Sodium  Hydroxide,  or  Caustic  Soda,  H  Na  O,  is  a  white 
solid  substance,  fusible  below  a  red  heat,  and  less  volatile 
than  the  corresponding  potassium  compound.  It  is  very  solu 
ble  in  water,  acts  as  a  caustic,  is  powerfully  alkaline,  and  is 
largely  used  in  soap-making.  The  manufacture  of  solid  caus 
tic  soda  is  now  carried  on  on  a  large  scale,  by  boiling  lime  and 
sodium  carbonate  together  with  water,  and  evaporating  down 
the  clear  solution. 

Ca  O  +  Na2  CO3  +  H2O  =  Ca  CO3  +  2(HNa  O). 

Sodium  Chloride — Common  Salt.  Na  Cl.  It  is  from  this 
salt  that  almost  all  the  other  sodium  compounds  are  prepared. 
Sodium  chloride  occurs  in  thick  beds  in  various  parts  of  the 
world,  especially  in  Cheshire,  Galicia,  Tyrol,  Spain,  and 
Transylvania.  It  is  likewise  prepared  from  sea- water  by 
evaporation  or  by  freezing  ;  and  from  certain  brine  springs  by 
evaporation.  When  slowly  deposited  sodium  chloride  crys 
tallizes  in  regular  cubes,  it  is  soluble  in  about  two  and  a  half 
parts  of  water  at  15°,  and  does  not  dissolve  sensibly  more  in 
hot  than  in  cold  water. 

Sodium  Carbonate,  Na2  COs.  This  substance,  known  in 
commerce  as  soda-ash,  is  manufactured  in  England  on  an 
enormous  scale,  and  used  for  glass-making,  soap-making, 
bleaching,  and  various  other  purposes  in  the  arts.  Formerly 
it  was  prepared  from  barilla  or  the  ashes  of  sea-plants,  but 
now  it  is  wholly  obtained  from  sea-salt  by  a  series  of  chemical 
decompositions  and  processes,  which  may  be  divided  into  two 
stages. 

(i)  Manufacture  of  sodium  sulphate,  or  salt-cake,  from 
sodium  chloride  (common  salt)  ;  called  salt-cake  process. 


Elementary  Chemistry.  163 

(2)  Manufacture  of  sodium  carbonate,  or  soda  ash,  from 
salt  cake  ;  called  soda-ash  process. 

(i)  Salt-cake  process.  This  process  consists  in  the  decom 
position  of  salt  by  means  of  sulphuric  acid  :  this  is  effected  in 
a  furnace  called  the  Salt-cake  Furnace.  Fig.  52  shows  the 
section,  and  Fig.  53  the  elevation  of  such  a  furnace  :  these  are 


FIG.  52. 


FIG.  53. 

drawn  to  scale  from  one  actually  in  use.  It  consists  of  (i)  a 
large  covered  iron  pan  placed  in  the  centre  of  the  furnace, 
and  heated  by  a  fire  placed  underneath  ;  and  (2)  two  roasters 
or  reverberatory  furnaces,  placed  one  at  each  end,  and  on  the 
hearths  of  which  the  salt  is  completely  decomposed.  The 
charge  of  half  a  ton  of  salt  is  first  placed  in  the  iron  pan,  and 
then  the  requisite  quantity  of  sulphuric  acid  allowed  to  run  in 
upon  it.  Hydrochloric  acid  gas  is  evolved,  and  escapes 
through  a  flue  with  the  products  of  combustion  into  towers, 
or  scrubbers,  filled  with  coke  or  bricks  moistened  with  a 
stream  of  water  ;  the  whole  of  the  acid  vapors  are  thus  con 
densed,  and  the  smoke  and  heated  air  pass  up  the  chimney. 
After  the  mixture  of  salt  and  acid  has  been  heated  for  some 
time  in  the  iron  pan,  and  has  become  solid,  it  is  raked  by 
means  of  the  doors  seen  in  Fig.  53,  on  to  the  hearths  of  the 
furnaces  at  each  side  of  the  decomposing  pan,  where  the 


1 64 


Elementary  Chemistry. 


flame  and  heated  air  of  the  fire  complete  the  decomposition 
into  sodium  sulphate  and  hydrochloric  acid. 

(2)  Soda  Ash  process.  This  process  consists  (i)  in  the 
preparation  of  sodic  carbonate,  and  (2)  in  the  separation  and 
purification  of  the  same.  The  first  chemical  change  which 
the  salt-cake  undergoes  in  its  passage  to  soda-ash,  is  its 
reduction  to  sulphide  by  heating  it  with  powdered  coal  or 
slack : 

Naa  SO4  +  C,  =  Naa  S  +  4  CO. 

The  second  decomposition  is  the  conversion  of  the  sodium 
sulphide  into  sodium  carbonate,  by  heating  it  with  chalk  or 
limestone  (calcium  carbonate)  : 

Na2S  +  Ca  CO3  =  Na2  CO3  +  Ca  S. 

These  two  reactions  are  in  practice  carried  on  at  once  ;  a 
mixture  of  ten  parts  of  salt  cake,  ten  parts  of  limestone,  and 
seven  and  a  half  parts  of  coal  being  heated  in  a  reverberatory 
furnace  called  the  Balling  Furnace  (shown  in  section  in  Fig. 
54,  and  in  elevation  in  Fig.  55),  until  it  fuses  and  the  above 


FIG.  54. 


FIG.  55- 

decomposition  is  complete,  when  it  is  raked  out  into  iron 
wheelbarrows  to  cool.  This  process  is  generally  termed  the 
black-ash  process,  from  the  color  of  the  fused  mass. 

The  next  operation  consists  in  the  separation  of  the  sodic 
carbonate  from  the  insoluble  calcium  sulphide  and  other  im- 


Elementary  Chemistry.  165 

purities.  This  is  easily  accomplished  by  lixiviation,  or  dis 
solving  the  former  salt  out  in  water.  On  evaporating  down  the 
solution,  for  which  the  waste  heat  of  the  black-ash  furnace  is 
used,  the  heated  air  passes  over  a  leaden  pan  (shown  in  Fig. 
54)  containing  the  liquid.  On»calcining  the  residue,  the  soda- 
ash  of  commerce  is  obtained.  No  less  than  200,000  tons  of 
common  salt  are  annually  consumed  in  the  alkali  works  of 
Great  Britain,  for  the  preparation  of  nearly  the  same  weight 
of  soda-ash,  of  which  the  value  is  about  two  millions  sterling. 
The  soda-ash  of  commerce  contains  from  48  to  56  per  cent, 
of  pure  caustic  soda,  Na^O,  as  carbonate  and  hydrate,  the 
remainder  being  impurities,  consisting  generally  of  sulphate, 
sulphite,  and  chloride.  If  soda-ash  be  dissolved,  and  the 
saturated  solution  allowed  to  stand,  large  transparent  crystals 
(monoclinic)  of  the  hydrated  carbonate,  of  the  formula  Na2 
COs  +  ioH2O  separate  out ;  this  substance  is  commonly 
known  as  soda-crystals,  and  is  much  used  for  softening  water 
for  washing  purposes. 

Hydric- Sodium  Carbonate,  or  Bicarbonate  of  Soda,  H  Na 
CO3,  is  obtained  by  exposing  the  crystallized  carbonate  in  an 
atmosphere  of  carbonic  acid  gas.  It  is  a  white  crystalline 
powder,  which  on  heating  is  readily  converted  into  sodium 
carbonate.  The  bicarbonate  is  chiefly  used  in  medicine,  and 
for  the  production  of  effervescing  drinks. 

The  other  sodium  salts  of  importance  are  sodium  nitrate  or 
Chili  saltpetre,  Na  NOs,  found  in  Northern  Chili  in  large 
beds,  imported  in  large  quantities,  and  chiefly  used  as  a 
manure  ;  sodium  sulphate,  or  Glauber  salts,  Na2  SO4  +  ioH2 
O  (in  the  anhydrous  state  known  as  salt-cake)  ;  hydric  sodium 
sulphate  (or  bisulphate),  H  Na  SC>4 ;  sodium  hyposulphite, 
Na2S2H2O4  +  4  H2  O,  mentioned  under  the  compounds  of 
sulphur  and  oxygen  (p.  113);  the  sodium  phosphates,  men 
tioned  under  phosphorus  (p.  130);  borax,  Na2O  2B2O3  +  io 
H2O  (see  p.  125);  sodium  sulphide,  Na2  S,  a  soluble  salt 
formed  by  reducing  the  sulphate  with  carbon  ;  sodium  sili 
cates',  or  soluble  glass  (see  p.  175). 

General  Characteristics  of  the  Sodium,  Compounds.     All 


1 66  Elementary  Chemistry. 

the  sodium  salts,  with  the  single  exception  of  the  antimoniate, 
are  soluble  in  water.  The  presence  of  sodium  compounds 
can  be  detected  by  the  peculiar  yellow  tinge  which  they  im 
part  to  the  flame.  The  spectrum  of  sodium  is  distinguished 
by  one  fine  bright  double  line,  identical  in  position  with  the 
dark  solar  line  called  D. 

3  and  4.  CESIUM  AND  RUBIDIUM.  Cae  =  133.  Rb  = 
85-4. 

These  two  metals  were  discovered  in  1 860-61  by  Bunsen 
and  Kirchoff,  by  means  of  spectrum  analysis  (see  p.  221). 
They  so  closely  resemble  one  another  and  potassium  in  their 
chemical  properties,  that  they  had  previously  been  mistaken 
for  the  latter  well-known  metal.  They  occur  widely  dis 
tributed,  although  generally  occurring  in  small  quantities. 
They  were  originally  discovered  in  the  mineral  water  of 
Durkheim,  but  since  that  time  they  have  been  found  in  many 
other  springs,  in  several  kinds  of  mica  and  other  old  plutonic 
silicates,  as  well  as  in  the  ashes  of  several  plants,  viz.  beet 
root,  tobacco,  coffee,  and  grapes.  These  metals  can  be 
separated  from  potassium  by  the  greater  insolubility  of  the 
double  chloride  which  they  form  with  platinum  ;  if  a  mixture 
of  K,  Cae,  and  Rb  salts  be  completely  precipitated  by  platinic 
chloride  and  the  precipitate  boiled  out  with  water,  the  insolu 
ble  residue  will  contain  the  new  metals.  Caesium  may  be 
separated  from  rubidium  by  the  greater  solubility  of  the  acid 
tartrate  of  the  former  metal.  The  salts  of  caesium  and  rubi 
dium  are  isomorphous  with  the  corresponding  potassium  com 
pounds.  The  fused  chlorides  of  these  metals  are  easily 
decomposed  by  the  galvanic  current,  and  the  metallic  element 
deposited.  The  metals  can  also  be  prepared  by  reduction 
with  carbon,  as  potassium.  Rubidium  is  a  white  metal  which 
rapidly  undergoes  oxidation,  its  specific  gravity  is  1-52,  and  it 
forms  a  greenish-blue  vapor.  Caesium  is  the  most  electro 
positive  of  the  metals. 

5.  LITHIUM.  Symbol  Li.  Combining  Weight  7.  Specific 
Gravity  0*59. 


Elementary  Chemistry.  167 

This  metal  is  prepared  by  decomposing  the  fused  chloride 
by  electricity;  it  is  of  a  white  color,  it  fuses  at  180°,  and  is 
the  lightest  metal  known.  The  lithium  salts  were  formerly 
supposed  to  be  very  rare,  only  being  known  to  occur  in  three 
or  four  minerals,  but  spectrum  analysis  has  shown  that  this  is 
a  widely-distributed  substance  ;  it  occurs  in  small  quantities 
in  almost  all  waters,  in  milk,  tobacco,  and  even  in  human 
blood.  A  spring  in  Cornwall  contains  large  quantities  of  this 
metal  in  the  form  of  chloride.  Lithium  in  its  chemical  rela 
tions  stands  between  the  class  of  alkaline  and  alkaline-earth 
metals,  the  hydrate,  carbonate,  and  phosphate,  being  only 
sparingly  soluble  in  water.  All  the  volatile  lithium  com 
pounds  impart  a  magnificent  crimson  tinge  to  the  flame,  and 
the  spectrum  of  this  flame  exhibits  the  presence  of  one  bright 
and  very  characteristic  red  line,  by  means  of  which  the  pres 
ence  of  the  minutest  trace  of  this  substance  can  be  detected 
with  certainty  and  ease. 

6.  AMMONIUM  AND  THE  SALTS  OF  AMMONIA. 
With  the  class  of  alkaline  metals  the  ammoniacal  salts  may 
conveniently  be  considered,  as  in  their  chemical  properties 
they  present  a  remarkable  analogy  with  the  salts  of  the  alka 
lies  proper.  In  all  these  salts  the  existence  of  a  quasi-metal 
called  Ammonium,  NH4,  is  supposed,  and  if  this  substance 
be  substituted  for  an  atom  of  potassium  or  sodium  in  the 
alkaline  salts,  a  corresponding  salt  of  ammonium  is  formed 
thus: 

Potassium  chloride,  KC1. 

Ammonium  chloride,  NH4  Cl. 

Potassium  sulphate,  K3  SO4. 

Ammonium  sulphate,  2  (NH4)  SO4. 

Ammonium  itself  has  not  yet  been  prepared  in  the  pure 
state,  but  an  amalgam  of  ammonium  and  mercury  is  known, 
and  the  existence  of  this  compound  appears  to  show  that  the 
body  NH4  acts  like  a  metal.  The  most  important  of  the 
ammoniacal  salts,  which  are  all  volatile,  are  ammonium- 
chloride,  or  sal-ammoniac,  NH4  Cl,  originally  prepared  by 


1 68  Elementary  Chemistry. 

subliming  camel's  dung,  but  now  obtained  by  neutralizing  the 
ammoniacal  water  of  the  gas  works  (see  p.  80)  with  hydro 
chloric  acid,  evaporating  the  liquor  to  dryness,  and  by  sub 
liming  the  volatile  sal-ammoniac.  The  sulphate,  2  (NH4) 
SC>4,  is  likewise  prepared  from  gas-liquor  by  neutralization 
with  sulphuric  acid.  The  carbonate,  nitrate,  and  sulphide  of 
ammonium  correspond  closely  to  the  same  potassium  salts. 
The  salts  of  ammonia  can  easily  be  recognized  by  their  giving 
off  an  alkaline  gas  possessing  a  pungent  smell  of  ammonia 
when  they  are  heated  with  caustic  lime  or  a  caustic  alkali. 
The  acid  tartrate  and  the  double  platinic  chloride  are  both 
insoluble,  and  resemble  the  corresponding  potash  cympounds 
so  closely  that  the  two  sets  of  salts  cannot  be  distinguished 
by  means  of  these  tests.  In  order  to  test  for  potash  in  pres 
ence  of  ammoniacal  salts,  all  the  latter  must  first  be  driven  off 
by  heating.* 


LESSON   XX. 

CLASS  II.    METALS  OF  THE  ALKALINE  EARTHS. 

These  are  three  in  number—  i.  CALCIUM,  2.  STRONTIUM, 
and  3.  BARIUM  ;  they  chiefly  differ  from  the  preceding  metals 
by  forming  insoluble  carbonates,  sulphates,  phosphates,  and 
oxalates. 

i.  CALCIUM.  Symbol  Ca.  Combining  Weight  40.  Spe 
cific  Gravity  1-58. 

Calcium  forms  a  considerable  portion  (see  p.  8)  of  the  plu- 
tonic  rocks  of  which  the  earth  is  composed,  and  occurs  in 
very  large  quantities,  forming  whole  mountain  chains  of  lime 
stone,  chalk,  gypsum,  and  mountain  limestone.  The  metal 

*  Ammonia,  NHs,  is  only  the  first  term  of  a  series  of  volatile  bodies  possessing 
closely-similar  properties  and  forming  definite  salts;  these  bodies  will  be  described 
in  the  part  relating  to  organic  chemistry. 


Elementary  Chemistry.  169 

calcium  is  obtained  by  the  decomposition  of  the  chloride  by 
the  electric  current,  or  by  heating  the  iodide  with  sodium  ;  it 
is  a  light  yellow  metal  which  easily  oxidizes  in  the  air,  and 
when  heated  in  air  it  burns  with  a  bright  light — lime,  CaO, 
the.  only  oxide  of  calcium,  being  formed. 

Calcium  Oxide,  or  Lime,  CaO.  Pure  lime  is  obtained  by 
heating  white  or  black  marble  to  redness  in  a  vessel  exposed 
to  the  air.  Lime  is  prepared  on  a  large  scale  for  building  and 
other  purposes,  by  heating  limestone  (the  carbonate)  in  kilns 
by  means  of  coal  mixed  with  the  stone  ;  the  carbonic  acid 
escapes,  and  quick-  or  caustic-lime,  remains.  Pure  lime  is  a 
white  infusible  substance,  which  combines  with  water  very 
readily,  giving  off  great  heat,  and  falling  to  a  white  powder 
called  calcium  hydrate,  or  slacked  lime,  CaO  H2O.  The 
hydrate  is  slightly  soluble  in  water,  I  part  of  it  dissolving  in 
730  parts  of  cold,  but  only  in  1300  parts  of  boiling  water,  and 
forming  lime-water,  which,  like  the  hydrate,  has  a  great  power 
of  absorbing  carbonic  acid  from  the  air.  It  is  indeed  partly 
owing  to  this  property  that  the  hardening  or  setting  of  mortars 
and  cements  made  from  lime  is  due.  Mortar  consists  of  a 
mixture  of  slacked  lime  and  sand  ;  a  gradual  combination  of 
the  lime  with  the  silica  occurs,  and  this  helps  to  harden  the 
mixture.  Hydraulic  mortars,  which  harden  under  water,  are 
prepared  by  carefully  heating  an  impure  lime  containing 
clay  and  silica;  a  compound  silicate  of  lime  and  alumina 
appears  to  be  formed  on  moistening  the  powder,  which 
then  solidifies,  and  is  unacted  upon  by  water.  Lime  is 
largely  used  in  agriculture,  its  action  being,  1st,  to  destroy 
the  excess  of  vegetable  matter  contained  in  the  soil ;  and, 
2dly,  to  liberate  the  potash  for  the  use  of  the  plants  from  heavy 
clay  soils  by  decomposing  the  silicate. 

Calcium  Carbonate,  or  Carbonate  of  Lime,  Ca  CO3.  This 
salt  occurs  most  widely  diffused,  as  chalk,  limestone,  coral, 
and  marble  ;  many  of  those  enormous  deposits  being  made 
up  of  the  microscopic  remains  of  minute  sea-animals.  Calcium 
carbonate  exists  crystalline  as  calc  spar,  or  Iceland  spar 
(rhombohedral,  or  hexagonal  system,  Fig.  45),  and  also  in  a 

8 


170  Elementary  Chemistry. 

different  form,  arragonite  (rhombic,  Fig.  46),  so  that  this  sub 
stance  is  dimorphous.  The  carbonate  is  almost  insoluble  in 
pure  water,  but  readily  dissolves  when  the  water  contains  car 
bonic  acid,  giving  rise  to  what  is  termed  temporarily  hard 
water.  Such  a  water  deposits  a  crust  of  calcium  carbonate 
on  boiling,  owing  to  the  escape  of  the  carbonic  acid.  The 
well-known  evil  of  boiler  crust  is  caused  by  these  deposits  : 
the  formation  of  such  a  crust  may  be  checked  if  not  avoided 
by  adding  a  small  quantity  of  sal-ammoniac  to  the  water, 
soluble  calcium  chloride  and  volatile  ammonium  carbonate 
being  formed.  Water  hard  with  dissolved  carbonate  may  be 
softened  by  the  addition  of  lime  suspended  in  water  in 
such  quantity  that  the  excess  of  carbonic  acid  is  neutra 
lized. 

Calcium  Sulphate,  Ca  SO4.  This  occurs  in  nature  as  a 
mineral  termed  Anhydrite,  and  combined  with  2  H2O  as 
selenite,  gypsum,  or  alabaster.  It  is  soluble  in  400  parts  of 
water,  and  is  a  very  common  impurity  in  spring  water,  giving 
rise  to  what  is  termed  permanent  hardness,  as  it  cannot  be 
removed  by  boiling.  Gypsum  when  moderately  heated  loses 
its  water,  and  is  then  called  plaster  of  Paris  ;  this  when 
moistened  takes  up  two  atoms  of  water  again  and  sets  to  a 
solid  mass,  and  is  therefore  much  used  for  making  casts  and 
moulds. 

Calcium  Chloride,  Ca  C12.  This  soluble  salt  is  formed 
when  limestone  or  marble  is  dissolved  in  hydrochloric  acid 
(see  p.  70) ;  if  the  solution  be  then  evaporated,  colorless 
needle-shaped  crystals  of  the  hydrated  chloride,  Ca  C13  +  6 
H2O,  are  formed.  When  these  are  dried  the  substance  still 
retains  2  H2O,  and  forms  a  porous  mass  which  takes  up 
moisture  with  great  avidity,  and  is  much  used  for  drying  gases. 
When  this  mass  is  more  strongly  heated  it  fuses  and  parts 
with  all  its  water. 

Calcium  Fluoride,  Fluor  spar,  Ca  Fa.  Found  crystallized 
in  cubes  in  Derbyshire  and  Cumberland.  When  heated  with 
sulphuric  acid,  calcium  sulphate  ai*d  hydrofluoric  acid  (see  p. 
100)  are  formed.  It  is  sometimes  used  as  a  flux  in  the  reduc- 


Elementary  Chemistry.  171 

tion  of  metals,  whence  its  name  Fluor  Spar  is  derived.  The 
foregoing  are  the  most  important  salts  of  calcium. 

Among  the  remaining  compounds  of  calcium  may  be 
mentioned  bleaching-powder,  or  chloride  of  lime,  Ca  Cla  Ca 
2  CIO,  the  properties  and  mode  of  preparation  of  which  salt  are 
described  on  p.  92;  calcium  phosphate,  or  bone -phosphate, 
Cas  2  PO*  (see  p.  129)  ;  calcium  sulphide,  Ca  S,  an  insoluble 
substance  formed  in  the  soda-ash  process  (see  p.  164);  and 
calcium  penta-sulphide,  Ca  85,  a  soluble  salt.  The  spectrum 
of  calcium  is  a  very  peculiar  one,  containing  a  number  of 
distinct  bright  lines  by  which  the  presence  of  this  metal  can 
be  easily  ascertained. 

2.  STRONTIUM.     Symbol  Sr.     Combining  Weight  87-5. 

This  element  occurs  in  much  smaller  quantities  than  cal 
cium,  or  even  barium,  being  found  in  only  a  few  mineral 
species,  especially  strontianite  the  carbonate,  and  celestine 
the  sulphate.  Strontium  likewise  occurs  in  minute  quantities 
in  certain  spring  waters.  The  metal  has  a  yellowish-white 
color,  and  is  prepared  by  the  action  of  a  current  of  electricity 
on  the  fused  chloride.  It  resembles  calcium  closely  in  its 
properties  ;  its  specific  gravity  is  2-54.  When  heated  in  the 
air  it  burns,  forming  the  monoxide  strontia. 

Strontium  Oxide,  or  Strontia,  Sr  O.  This  oxide  is  best 
obtained  by  decomposing  the  nitrate  by  heat ;  it  unites  with 
water,  evolving  great  heat,  and  forming  the  hydrate  Sr  O  + 
9  Ha  O ;  this  is  soluble  in  water,  and  absorbs  carbonic  acid 
with  avidity.  The  native  salts  of  strontium,  viz.,  the  car 
bonate  and  sulphate,  are  insoluble,  and  serve  for  the  prepara 
tion  of  the  remaining  salts.  The  nitrate,  Sr  2  NOa,  and  the 
chloride,  Sr  C12,  are  soluble  in  water ;  these  are  the  only 
salts  of  this  metal  which  are  employed  in  the  arts,  and  these 
are  used  for  the  preparation  of  red  fires,  as  the  volatile  salts 
of  strontium  "have  the  power  of  coloring  the  flame  crimson. 
The  spectrum  of  strontium  is  a  very  characteristic  one,  and 
by  this  means  the  minutest  trace  of  this  substance  can  be 
easily  and  certainly  detected,  even  in  presence  of  calcium  and 
barium  salts. 


172  Elementary  Chemistry. 

3    BARIUM.     Symbol  Ba.     Combining  Weight  137. 

Barium  compounds  occur  somewhat  more  widely  dispersed 
than  those  of  strontium,  the  two  most  common  barium  min 
erals  being  the  sulphate,  or  heavy  spar,  and  the  carbonate, 
or  witherite.  The  metal  barium  has  not  yet  been  obtained 
in  the  coherent  state,  but  the  metallic  powder  may  be  pre 
pared  in  a  similar  way  as  the  two  former  metals,  which  it 
closely  resembles  in  its  properties. 

Barium  Monoxide,  or  Baryta,  Ba  O.  The  best  way  of 
forming  this  oxide  is  to  decompose  the  nitrate  by  heat ;  it 
is  a  grayish  porous  mass,  which  fuses  at  a  high  temperature, 
and  takes  up  water  with  evolution  of  much  heat,  forming  a 
crystalline  hydrate,  H2  Ba  O2  +  8  H2  O.  This  hydrate  is 
soluble  in  twenty  parts  of  cold  water,  and  the  solution  on 
exposure  to  the  air  rapidly  absorbs  carbonic  acid  and  be 
comes  milky. 

Barium  Dioxide,  Ba  Oa.  When  baryta  is  gently  heated  in 
a  current  of  oxygen  gas,  the  two  substances  combine  together 
to  form  a  dioxide  containing  twice  as  much  oxygen  as  baryta  ; 
this  additional  atom  of  oxygen  is,  however,  evolved  at  a  high 
er  temperature,  and  it  has  been  proposed  to  use  this  decom 
position  for  the  manufacture  of  oxygen  from  the  air.  For  this 
purpose,  as  soon  as  the  dioxide  BaO2  has  been  reduced  to  Ba 
O,  the  temperature  is  lowered,  and  air  passed  over  the  baryta ; 
this  again  takes  up  oxygen,  passing  into  Ba  Oa,  which  again  is 
decomposed  by  a  higher  temperature.  This  interesting  pro 
cess  has,  however,  been  found  not  to  work  in  practice.  There 
are  no  salts  known  corresponding  to  this  oxide. 

Barium  Chloride,  Ba  Cla.  This  soluble  salt  is  one  of  the 
most  important  compounds  of  barium  ;  it  crystallizes  in  flat 
scales  containing  two  atoms  of  water.  It  may  be  prepared  by 
dissolving  the  native  carbonate  in  hydrochloric  acid,  and  it  is 
largely  used  as  a  precipitant  for  sulphuric  acid.  Barium  Sul 
phate,  Ba  SO4,  occurs  native  and  crystalline  as  heavy  spar ; 
specific  gravity  4-6  (whence  the  name  Barium,  from  jSapij 
(heavy).  It  is  one  of  the  most  insoluble  salts  known,  and  falls 
as  a  white  crystalline  precipitate  when  any  soluble  barium  salt 


Elementary  Chemistry.  173 

is  brought  into  a  solution  of  a  sulphate.  It  is  used  as  a  paint, 
and  the  precipitated  salt  is  termed  blancfixe,  whilst  the  na 
tive  heavy  spar,  when  ground,  is  largely  used  to  adulterate 
white  lead  (see  p.  205). 

The  other  more  important  salts  of  barium  are  the  nitrate 
Ba  2  NO3,  a  soluble  salt ;  the  sulphide,  a  soluble  salt,  BaS, 
obtained  by  heating  heavy  spar  with  coal  and  dissolving  in 
water ;  the  carbonate,  Ba  CO3,  an  insoluble  substance,  occur 
ring  native  as  witherite  :  the  silicofluoride  and  the  phosphate 
are  insoluble  salts,  whilst  strontium  silicofluoride  is  soluble  in 
water.  The  volatile  salts  of  barium  have  the  power  of  com 
municating  a  peculiar  green  color  to  the  flame,  and  the  spec 
trum  of  barium  contains  a  number  of  characteristic  green 
lines,  by  means  of  which  the  presence  of  minute  traces  of  this 
substance  can  be  detected. 


CLASS  III.    METALS  OF  THE  EARTHS. 

I.  ALUMINIUM.  Symbol  Al.  Combining  Weight  27-4. 
Specific  Gravity  2'6. 

This  metal  occurs  in  large  quantities  combined  with  silicon 
and  oxygen  in  felspar  and  all  the  older  rocks,  and  also  in 
clay,  marl,  slate,  and  in  many  crystalline  minerals.  Metallic 
aluminium  is  obtained  'by  passing  the  vapor  of  aluminium 
chloride  over  metallic  sodium.  It  has  recently  been  manufac 
tured  on  a  large  scale  both  in  England  and  France,  and,  from 
its  lightness  (specific  gravity  2*6)  and  its  bright  lustre,  it  has 
been  used  for  optical  purposes  as  well  as  for  ornamental  work. 

Alumina,  A12  O8,  specific  gravity,  3*9.  This  is  the  only 
oxide  of  aluminium  known.  It  occurs  native  in  a  nearly  pure 
and  crystalline  state  as  corundum,  ruby,  sapphire,  and  emery. 
Alumina  is  prepared  by  adding  ammonia  to  a  solution  of 
alum  ;  a  white  precipitate  of  the  hydrate  falls  down,  and  this 
on  being  heated  yields  a  white  amorphous  powder  of  pure 
alumina.  This  substance  is  attacked  with  difficulty  by  acids, 
but  the  hydrate  is  easily  soluble  in  acids  and  in  the  fixed  caus 
tic  alkalies.  Alumina  acts  as  a  weak  base ;  the  commonest 


1/4  Elementary  Chemistry. 

aluminium  salts  are  the  alums,  and  their  solutions  have  an 
acid  re-action.  Alumina  is  largely  used  in  dyeing  and  calico- 
printing  as  a  mordant,  as  it  has  the  power  of  forming  insolu 
ble  compounds  called  lakes  with  vegetable  coloring  matter, 
and  thus  renders  the  color  permanent  by  fixing  it  in  the  pores 
of  the  cloth  so  that  it  cannot  be  washed  out ;  such  colors  are 
termed  fast. 

Aluminium  chloride,  A12  Cle,  is  a  volatile  white  solid  body, 
obtained  by  heating  a  mixture  of  alumina  and  charcoal  in  a 
current  of  chlorine  gas  ;  it  is  used  in  the  manufacture  of  the 
metal. 

The  soluble  aluminium  sulphate,  Ala  3804,  is  prepared  on  a 
large  scale  for  the  use  of  the  dyer  by  decomposing  clay  by  act 
ing  upon  it  with  sulphuric  acid  ;  the  solid  mixture  of  silica 
and  aluminium  sulphate  thus  obtained  goes  by  the  name  of 
alum-cake.  The  most  useful  compounds  of  alumina  are,  how 
ever,  the  alums,  a  series  of  double  salts,  which  aluminium  sul 
phate  forms  with  the  alkaline  sulphates.  Common  potash 
alum,  or  aluminium  potassium  sulphate,  has  the  composition 
A12  K2  4SC>4  +  24H2  O,  and  crystallizes  in  regular  octohedra 
(Fig.  38).  It  may  be  prepared  by  dissolving  the  two  sulphates 
together,  and  allowing  the  compound  salt  to  crystallize,  but  it 
is  usually  obtained  from  the  decomposition  of  a  shale  or  clay 
containing  iron  pyrites,  Fe  S3 ;  this  substance  gradually  un 
dergoes  oxidation  when  the  shale  is  roasted,  absorbs  oxygen 
from  the  air  producing  sulphuric  acid,  which  unites  with  the 
alumina  of  the  clay,  and  on  the  addition  of  a  potassium  com 
pound,  alum  crystallizes  out.  A  salt  called  ammonium  alum, 
and  containing  N  H4,  instead  of  K,  is  at  present  prepared  on 
a  large  scale,  the  ammonia  liquor  of  the  gasworks,  together 
with  sulphuric  acid,  being  added  to  the  burnt  shale,  instead 
of  a  potash  salt. 

There  are  a  large  number  of  other  alums  known,  in  which 
the  isomorphous  sesquioxides  of  iron,  chromium,  and  man 
ganese,  are  substituted  for  the  alumina  in  common  alum  ;  all 
these  alums  occur  in  regular  octohedra,  and  cannot  be  sepa 
rated  by  crystallization  when  present  in  solution  together. 


Elementary  Chemistry.  175 

Clay  is  an  aluminium-silicate  resulting  from  the  disintegration 
and  decomposition  of  felspar  by  the  action  of  air  and  water, 
the  soluble  alkali  being  washed  away.  Kaolin  or  porcelain 
clay  is  the  purest  form  of  disintegrated  felspar,  containing  no 
iron  or  other  impurities.  There  are  many  very  beautifully 
crystalline  minerals,  consisting  of  aluminium  silicates  com 
bined  with  silicates  of  the  metals  of  the  alkalies  and  alkaline 
earths  ;  amongst  others,  garnet,  idocrase,  mica,  lepidolite,  &c. 
Some  silicates,  such  as  stilbite,  analcime,  &c.,  retain  water  of 
crystallization,  and  are  termed  zeolites.  Aluminium  salts  can 
be  detected  when  in  solution  by  giving  with  ammonia  a  white 
precipitate,  insoluble  in  excess,  but  soluble  in  caustic  soda ; 
and  by  assuming  a  blue  color  when  moistened  with  cobalt  so 
lution  and  heated  before  the  blowpipe. 

Glass,  Porcelain,  and  Earthenware. 

The  silicates  of  the  alkalies  are,  as  we  have  seen,  soluble  in 
water  and  non-crystalline  ;  those  of  the  alkaline  earths  are 
soluble  in  acid  and  crystalline,  whilst  compounds  of  the  two 
are  insoluble  in  water  and  acids,  and  do  not  assume  a  crystal 
line  form.  Such  a  compound  when  fused  is  termed  a  glass. 
There  are  four  different  descriptions  of  glass  used  in 
the  arts,  differing  in  their  chemical  composition  and  ex 
hibiting  corresponding  differences  in  their  properties,  (i) 
Crown  or  window  and  plate-glass,  composed  of  silicates 
of  soda  and  lime.  (2)  Bohemian  glass,  consisting  of  si 
licates  of  potash  and  lime.  (3)  Flint-glass  or  crystal,  con 
taining  silicates  of  potash  and  lead  oxide ;  and  (4)  Common 
green  bottle-glass,  composed  of  silicates  of  soda,  lime,  oxide 
of  iron,  and  alumina.  The  first  and  third  of  these  kinds  of 
glass  are  easily  fusible,  whilst  the  second  or  potash  glass  is 
much  more  infusible  ;  the  addition  of  oxide  of  lead  increases 
the  specific  gravity,  and  the  lustre  of  the  glass,  as  well  as  its 
fusibility.  The  common  glass  articles  of  household  use  are 
generally  made  of  flint  glass,  whilst  for  chemical  apparatus  a 
soda-lime-glass  is  to  be  preferred.  The  potash-lime-glass  is 
much  employed  where  a  difficultly  fusible,  or  hard,  glass  is 


176  Elementary  Chemistry. 

needed,  as  for  instance  in  the  manufacture  of  combustion 
tubes  for  organic  analysis  (see  p.  236).  The  fourth  description 
of  glass  is  an  impure  mixture  of  various  silicates,  employed 
for  purposes  in  which  the  colors  and  fineness  of  the  glass  is 
not  of  consequence. 

In  the  preparation  of  all  the  fine  qualities  of  glass,  great 
care  is  requisite  in  the  selection  of  pure  materials,  as  well  as 
in  the  processes  of  manufacture ;  generally  the  materials  are 
melted  together  with  a  quarter  to  half  their  weight  of  "  cullet" 
or  broken  glass  of  the  same  kind.  After  the  glass  articles 
have  been  blown  or  cast,  they  must  all  be  exposed  to  the  pro 
cess  of  "annealing,"  or  slow  cooling,  otherwise  they  are  so 
brittle  as  to  be  perfectly  useless,  breaking  with  the  slightest 
touch,  owing  to  the  irregular  contraction  of  the  different 
parts  brought  about  by  rapid  cooling.  The  following  table 
shows  the  composition  of  the  chief  varieties  of  glass. 

INGREDIENTS  FOR  VARIOUS  GLASSES. 


L.rown  Lri 
Quartz  Sand  . 

ass. 
100  parts. 

Ml 

Pure  Sand 

rror  r 

late. 

100 

parts. 

Mild  Lime     .     . 

36 

» 

Soda  Ash 

. 

35 

» 

Soda  Ash      .      . 

24 

if 

Mild  Lime 

. 

5 

» 

Sodium  Sulphate 

12 

» 

Arsenious 

Oxide 

% 

» 

Arsenious  Oxide 

* 

» 

Cullet.      . 

IOO 

PI 

Cullet       .      .      . 

100 

» 

Bohemian  Glass. 

Flint  Glass. 

Pure  Sand 

100 

» 

Pure  Sand 

IOO 

» 

Pure  Pearlashes 

60 

H 

Red  Lead 

. 

20 

» 

Chalk      .      .      . 

8 

» 

Pearlash  . 

. 

40 

?» 

Cullet      .      .      . 

40 

» 

Nitre  .      . 

. 

2 

» 

Manganese  Dioxide  $ 

?> 

Cullet       . 

50  to 

IOO 

n 

Colored  Glass.  Certain  metallic  oxides  possess  the  power 
of  coloring  glass  when  they  are  added  in  small  quantity.  Thus 
ferrous  oxide  produces  a  deep  green  color  (bottle  glass),  whilst 
the  oxides  of  manganese  impart  a  purple  tint  to  glass  ;  these 
facts  are  made  use  of  in  the  preparation  of  colorless  glass,  for 
as  it  is  difficult  to  obtain  materials  perfectly  free  from  iron,  which 


Elementary  Chemistry.  177 

imparts  a  green  color,  a  small  quantity  of  manganese  dioxide 
is  added  to  the  mixture,  and  the  violet  color  thus  produced  is 
complementary  to  the  green,  and  a  nearly  colorless  glass  is 
the  result.  The  addition  of  arsenious  oxide  effects  the  same 
end  by  oxidizing  the  ferrous  to  ferric-oxide.  The  colors  of 
precious  stones  are  imitated  by  adding  certain  oxides  to  a 
brilliant  lead  glass  called  "  paste  ;"  thus  the  blue  of  the  sap 
phire  is  given  by  a  small  quantity  of  cobalt  oxide,  whilst  cu 
prous  oxide  imparts  a  ruby-red  color,  and  ferric  oxide  a  yel 
low  color  resembling  topaz. 

Porcelain  and  Earthenware.  The  various  forms  of  porce 
lain  and  earthenware  consist  of  silicate  of  alumina,  in  fact 
clay,  in  a  more  or  less  pure  state,  covered  with  some  sub 
stance  which  fuses  at  a  high  temperature,  and  forms  a  glaze, 
giving  a  smooth  surface  and  binding  the  material  together, 
and  thus  counteracting  the  porous  nature  of  the  baked  clay. 
For  the  manufacture  of  porcelain  the  finest  white  or  China 
clay  is  used,  resulting  from  the  gradual  decomposition  of  fel 
spar,  whilst  for  the  common  earthenware  a  colored  clay  may 
be  employed.  The  glaze  used  for  porcelain  is  generally  finely 
powdered  felspar,  the  biscuit  or  porous  ware  being  dipped  into 
a  vessel  containing  this  substance  suspended  in  water,  and 
then  strongly  fired.  The  articles  thus  coated  can  be  used  for 
chemical  purposes,  as  this  glaze  withstands  the  action  of 
acids.  •  For  earthenware  the  so-called  "salt  glaze"  is  used  ; 
the  mode  of  obtaining  this  glaze  consists  in  throwing  some 
common  salt  into  the  furnaces  containing  the  strongly  heated 
ware,  when  the  salt  is  volatilized  and  undergoes  decomposi 
tion  on  the  heated  surface,  causing  a  deposit  of  a  fusible  sili 
cate  upon  it,  and  rendering  the  ware  impervious  to  moisture. 

LESSON  XXI.      £^>  *3  / . 

CLASS  IV.     (i.)  MAGNESIUM.     (2.)  ZINC.    (/) '-CJLPMIUM. 
i.   MAGNESIUM.     Symbol  Mg.     Combining  Weight  '2^'O. 
Specific  Gravity  174. 


178  Elementary  Chemistry. 

This  metal  occurs  in  large  quantities  as  carbonate,  along 
with  calcium  carbonate,  in  dolomite  or  mountain  limestone, 
and  also  in  sea-water  and  certain  mineral  springs,  as  chloride 
and  sulphate.  The  metal  itself  has  only  recently  been  pre 
pared  in  quantity  ;  it  is  best  obtained  by  heating  magnesium 
chloride  with  metallic  sodium,  sodium  chloride  and  metallic 
magnesium  being  formed.  This  metal  is  of  a  silver-white 
color  and  fuses  at  a  low  red  heat,  it  is  volatile,  and  may  be 
easily  distilled  at  a  bright  red  heat ;  when  soft  it  can  be 
pressed  into  wire,  and  with  care  it  may  be  cast  like  brass, 
although  when  strongly  heated  in  the  air  it  takes  fire  and 
burns  with  a  dazzling  white  light,  with  the  formation  of  its 
only  oxide,  magnesia.  The  light  emitted  by  burning  magne 
sium  wire  is  distinguished  for  its  richness  in  chemically  active 
rays,  and  this  substance  is  therefore  employed  as  a  substitute 
for  sunlight  in  photography. 

Magnesium  does  not  oxidize  in  dry  air;  it  is  only  slowly 
acted  upon  by  cold  water,  but  more  rapidly  by  hot  water  ;  it 
rapidly  dissolves  in  sulphuric  and  hydrochloric  acids,  with 
evolution  of  hydrogen. 

Magnesium  Oxide,  or  Magnesia,  Mg  O.  A  light  white 
amorphous  infusible  powder,  obtained  by  heating  the  carbon 
ate  or  nitrate.  It  unites  with  acids  to  form  the  magnesium 
salts,  but  it  does  not  possess  a  strong  alkaline  reaction.  The 
most  important  salts  of  magnesium  are  : — Magnesium  Chlo 
ride,  Mg  Clj,  a  fusible  salt  obtained  by  heating  a  solution  of 
magnesia  in  hydrochloric  acid  with  an  equal  quantity  of  sal- 
ammoniac  ;  on  fusion,  the  latter  salt  volatilizes,  and  the  mag 
nesium  chloride  remains  behind.  Magnesium  Sulphate, 
Mg  SO4  +  7H2O  :  this  is  a  soluble  substance  known  as  Ep 
som  Salts  ;  it  occurs  in  a  spring  in  Surrey,  and  contains 
seven  atoms  of  water  of  crystallization  ;  it  is  now  largely 
made  from  dolomite  by  separating  the  lime  with  the  sulphuric 
acid.  Magnesium  sulphate  forms,  with  the  alkaline  sulphates, 
double  salts,  in  which  the  alkaline  sulphate  takes  the  place 
of  one  atom  of  water  of  crystallization  ;  thus,  MgSChKaSCX 
+  6H2O  is  the  potash  double  salt.  The  Carbonate,  MgCOs, 


Elementary  Chemistry.  179 

is  an  insoluble  compound,  occurring  as  a  crystallized  mineral 
termed  magnesite.  The  magnesia  alba  of  the  shops  is  a 
varying  mixture  of  carbonate  and  hydrate,  made  by  precipat- 
ing  a  hot  solution  of  magnesium  sulphate  with  sodium  car 
bonate.  Magnesium  sulphide  is  not  formed  in  the  wet  way. 
Magnesium  resembles  in  many  respects  the  metals  of  the 
alkaline  earths,  but  it  may  be  distinguished  from  these  by  the 
solubility  of  the  carbonate  in  ammonium  chloride,  as  well  as 
by  the  ready  solubility  of  the  sulphate  in  water.  Magne 
sium  forms  an  insoluble  double  phosphate  with  ammonia, 
Mg  NH4PO4  +  6H2O,  and  it  is  in  this  form  that  the  metal  is 
usually  estimated. 

2.  ZINC.  Symbol  Zn.  Combining  Weight  65 '2.  Specific 
Gravity  6*8  to  7*2. 

Zinc  is  an  abundant  and  useful  metal,  closely  resembling 
magnesium  in  its  chemical  characters  ;  but  it  is  much  more 
easily  extracted  from  its  ores  than  this  latter  metal.  The 
chief  ores  of  zinc  are  the  sulphide  or  blende,  the  carbonate 
or  calamine,  and  the  red  oxide.  In  order  to  extract  the 
metal  the  powdered  ore  is  roasted,  or  exposed  to  air  at  a  high 
temperature,  so  as  to  convert  the  sulphide  of  carbonate  or 
carbonate  into  oxide  ;  the  roasted  ore  is  then  mixed  with 
fine  coal  or  charcoal  and  strongly  heated  in  crucibles  or 
retorts  of  peculiar  shape  ;  the  zinc  oxide  is  reduced  by  the 
carbon,  carbonic  oxide  gas  comes  off,  and  the  metallic  zinc 
distils  over,  and  is  easily  condensed. 

Zinc  is  a  bluish- white  metal,  exhibiting  crystalline  structure  ; 
it  is  brittle  at  the  ordinary  temperature,  but  when  heated  to 
about  130°,  it  may  be  rolled  out  or  hammered  with  ease, 
whilst  if  more  strongly  heated  to  200°,  it  is  again  brittle,  and 
may  be  broken  up  in  a  mortar.  Zinc  melts  at  423°,  and  at  a 
bright  red  heat  it  begins  to  boil  and  volatilizes,  or  if  air  be 
present  it  takes  fire  and  burns  with  a  luminous  greenish  flame, 
forming  zinc  oxide.  Zinc  is  not  acted  upon  by  moist  or  dry 
air,  and  hence  it  is  largely  used  in  the  form  of  sheets,  and  is 
employed  as  a  protecting  covering  for  iron,  which  when  thus 


i8o  Elementary  Chemistry. 

coated,  is  said  to  be  galvanized.  Zinc  e^ily  dissolves  in 
dilute  acids  with  the  evolution  of  hydrogen,  and  it  is  thus 
used  as  the  oxidizable  portion  of  the  galvanic  battery.  Brass 
is  a  useful  alloy  of  one  part  of  zinc  and  two  of  copper  ; 
German  silver  is  an  alloy  of  zinc,  nickel,  and  copper. 

Zinc  Oxide,  Zn  O,  is  the  only  known  compound  of  this 
metal  with  oxygen,  and  is  obtained  by  burning  the  metal,  or 
by  precipitating  a  soluble  zinc  salt  with  an  alkali,  and  heating 
the  precipitate.  Zinc  oxide  is  an  insoluble  white  amorphous 
powder,  which  when  heated  becomes  yellow,  but  loses  this 
color  on  cooling  ;  it  dissolves  easily  in  acids,  giving  rise  to  the 
zinc  salts.  The  most  important  salts  of  zinc  are  :  Zinc  sul 
phate,  Zn  SO4  +  7  H2O,  a  soluble  salt,  crystallizing  in  long 
prisms,  and  commonly  called  white  vitriol  ;  this  salt  is  isomor- 
phous  with  magnesium  sulphate,  and  like  the  latter  salt  it 
forms  a  series  of  double  salts  with  alkaline  sulphates.  The 
chloride,  Zn  C12,  a  white  soluble,  deliquescent  substance, 
formed  by  buring  zinc  in  chlorine  ;  or  better,  by  dissolving 
the  metal  in  hydrochloric  acid.  The  sulphide,  Zn  S,  occurs  as 
a  crystalline  mineral  called  blende,  generally  colored,  from 
presence  of  iron  and  other  impurities  ;  it  is  obtained  arti 
ficially  as  a  white  gelatinous  precipitate,  insoluble  in  acetic, 
but  soluble  in  a  mineral  acid,  formed  when  an  alkaline  sul 
phide  is  added  to  a  soluble  zinc  salt.  The  carbonate,  Zn  CO3, 
an  insoluble  substance,  occurring  native  as  calamine :  it  can 
not  be  prepared  by  precipitating  a  solution  of  zinc  salt  by  an 
alkaline  carbonate,  as  a  quantity  of  oxide  is  precipitated  along 
with  the  carbonate.  The  salts  of  zinc  can  be  distinguished  by 
the  solubility  of  the  oxide  in  excess  of  both  potash  and  am 
monia  ;  by  the  white  sulphide  insoluble  in  acetic  acid,  and  by 
the  green  color  which  a  solution  of  cobalt  chloride  imparts  to 
these  salts  when  heated  before  the  blowpipe. 

3.  CADMIUM.  Symbol  Cd.  Combining  Weight  \\i.  Speci 
fic  Gravity  8'6. 

This  is  a  comparatively  rare  metal,  occurring  in  certain  zinc 
ores.  In  its  chemical  relations  it  closely  resembles  zinc.  It 


Elementary  Chemistry.  181 

is,  however,  more  volatile  than  the  other  metal,  and  therefore 
distils  over  first  in  the  preparation  of  zinc.  Cadmium  is  a 
white  ductile  metal,  melting  at  315°  ;  it  may  be  easily  dis 
tinguished  and  separated  from  zinc  by  yielding  a  bright  yel 
low  sulphide  insoluble  in  hydrochloric  acid.  The  metal  takes 
fire  when  heated  in  the  air,  forming  a  brown  oxide,  Cd  O. 
The  chloride  and  sulphate  are  soluble  well-crystallizing  salts. 
Cadmium  iodide  is  occasionally  used  in  photography,  and  the 
yellow  sulphide  has  been  employed  as  a  pigment. 

CLASS  V.  IRON  CLASS. — i,  MANGANESE.  2,  IRON.  3, 
COBALT.  4,  NICKEL.  5,  CHROMIUM.  6,  URANIUM.  7, 
INDIUM. 

i.  MANGANESE.  Symbol  Mn.  Combining  Weight  55, 
Specific  Gravity  8-o. 

Manganese  occurs  in  nature  as  an  oxide,  and  it  can  be  ob 
tained,  though  with  difficulty,  in  the  metallic  state  by  heating 
the  oxide  very  strongly  with  charcoal.  The  metal  is  of  a  red 
dish-white  color;  it  is  brittle,  and  hard  enough  to  scratch 
glass.  It  decomposes  water  at  the  ordinary  temperature  with 
evolution  of  hydrogen  ;  it  cannot  be  preserved  in  the  air 
without  undergoing  oxidation,  and  must  be  kept  under  naph 
tha,  or  in  a  sealed  tube  ;  it  is  slightly  magnetic,  and,  like  iron, 
combines  with  carbon  and  silicon.  Metallic  manganese  is  not 
used  in  the  arts,  but  an  alloy  of  this  metal  and  iron  is  now 
made  on  a  large  scale,  and  used  in  the  manufacture  of  steel. 
Some  of  its  oxides  are  used  for  the  purpose  of  evolving  chlo 
rine  from  hydrochloric  acid,  and  also  for  tinting  glass  a  purple 
color. 

Manganese  forms  several  well-characterized  oxides :  (i) 
Manganous  oxide,  or  manganese  monoxide,  MnO,  is  a  basic 
body,  furnishing  the  series  of  well-known  manganous  salts,  in 
which  the  oxygen  is  replaced  by  its  equivalent  of  another 
element,  or  of  a  salt  radical ;  thus,  MnO,  MnCl2,  MnSO4, 
Mn2  NO3  ;  (2)  manganic  oxide,  or  manganese  sesquioxide, 
Mn2O»,  which  also  forms  salts,  but  of  a  much  less  stable 


1 82  Elementary  Chemistry. 

character,  and  occurs  in  nature  as  the  mineral  braunite  :  (3) 
red,  or  mangano-manganic  oxide,  Mn3O4,  a  neutral  body,  cor 
responding  to  the  magnetic  oxide  of  iron,  and  occurring  in 
nature  as  hausmannite  ;  (4)  black  oxide,  or  manganese  dioxide, 
MnO2,  a  neutral  substance,  occurring  as  the  ore  of  manganese 
in  the  minerals  pyrolusite  and  varvacite  ;  (5)  and  (6)  two 
compounds  of  manganese  and  oxygen  which  have  not  been 
prepared  in  the  anhydrous  state,  but  of  which  the  acids  cor 
responding  are  known  in  combination  as  salts  ;  thus  we 
have  K2MnO.j,  potassium  manganate,  and  KMnO-j,  potassium 
permanganate. 

Manganous  Oxide,  MnO,  is  a  greenish  powder,  obtained  by 
heating  the  carbonate  in  absence  of  air  ;  it  forms,  with  acids, 
a  series  of  pink-colored  salts,  and  rapidly  absorbs  oxygen, 
passing  into  a  higher  state  of  oxidation.  The  hydrate  is 
precipitated  as  a  white  gelatinous  mass,  when  an  alkali  is 
added  to  a  solution  of  manganous  salt ;  this,  however,  rapidly 
becomes  brown,  owing  to  absorption  of  oxygen.  Of  the 
manganous  salts,  the  chief  soluble  ones  are,  the  sjdphate, 
MnSC>4  +  5H2O,  a  pink-colored  crystalline  salt,  prepared  by 
acting  on  the  dioxide  with  sulphuric  acid,  oxygen  gas  being 
evolved, 

MnOa  +  H2SO4  =  MnSO4  +  O  +  H2O  ; 

the  chloride,  MnCla  +  4  HSO,  is  a  salt  obtained  by  crystalli 
zation  from  the  residues  in  the  manufacture  of  chlorine  from 
the  dioxide  and  hydrochloric  acid, 

MnO2  +  4  HC1  =  MnCl2  +  2H2O  +  C12. 

Among  the  insoluble  manganous  salts  of  importance  are  the 
sulphide,  MnS,  obtained  as  a  flesh-colored  precipitate  by  the 
addition  of  an  alkaline  sulphide  to  a  soluble  manganous  salt ; 
and  the  carbonate,  MnCO3,  which  occurs  native,  crystallizing 
like  calcspar  in  rhombohedra,  and  is  prepared  as  a  white 
powder  by  precipitating  a  manganous  salt  by  an  alkaline 
carbonate. 

Manganese  Sesquioxide,  Mn2  O3;  exists  in  nature  as  braun- 


Elementary  Chemistry.  183 

ite,  and  may  be  prepared  artificially  by  exposing  manganous 
oxide  to  a  red  heat.  It  forms  a  series  of  somewhat  unstable 
salts,  of  which  the  manganese  alum  is  one  of  the  most  inter 
esting,  being  isomorphous  with  common  alum,  in  which 
Mn2  O3  is  substituted  for  A12O3. 

«.  Manganese  Dioxide,  Mn  O2,  is  the  common  black  ore  of 
manganese,  and  is  termed  pyrolusite  by  mineralogists  ;  it 
can  be  artificially  formed  by  adding  a  solution  of  bleaching 
powder  to  a  manganous  salt.  This  substance  yields  one-third 
of  its  oxygen  when  heated  to  redness  (see  p.  n),  forming  the 
red  oxide,  3  MnO2  =  Mn3O4  +  O2,  and  gives  up  half  its  oxy 
gen  when  heated  with  sulphuric  acid  (see  above.)  It  is  largely 
used  for  the  manufacture  of  chlorine. 

Manganic,  and  Per-manganic  Acids.  When  an  oxide  of 
manganese  is  fused  with  caustic  alkali,  a  bright  green  mass 
is  formed,  which  yields  a  dark  green  solution  ;  this  contains 
potassium  manganate,  K2MnO4,  which  may  be  crystallized, 
and  is  isomorphous  with  the  corresponding  sulphate  and 
chromate.  If  this  green  solution  be  allowed  to  stand,  it 
slowly  changes  to  a  bright  purple  color,  and  hydrated  man 
ganic  dioxide  is  deposited,  hence  its  common  name  of  mine 
ral  chamelion  :  it  then  contains  a  new  salt  in  solution,  viz.  a 
per-manganate,  KMnO4,  which  may  be  obtained  in  the  crys 
talline  state  by  evaporation,  and  is  isomorphous  with  potas 
sium  perchlorate.  The  presence  of  a  few  drops  of  acid  at 
once  effects  this  decomposition  on  the.  green  solution. 

The  manganates  and  per-manganates  readily  give  up  a  part 
of  their  oxygen  in  presence  of  organic  matter,  and  they  are 
now  largely  used  as  disinfectants,  and  known  as  Condy's 
liquids,  as  well  as  being  employed  in  the  laboratory  for  the 
purpose  of  volumetric  analysis.  Manganese  is  chiefly  charac 
terized  by  the  flesh-colored  sulphide,  and  by  the  formation  of 
the  green  sodium  manganate,  a  most  delicate  reaction. 

.  i;  v 

V  K  Ks  I  TV   (t  |. 


184  Elementary  Chemistry. 


LESSON  XXII. 

2.  IRON.  Symbol  Fe.  Combining  Weight  65.  Specific 
Gravity  7*8. 

Iron  is  of  all  metals  the  most  important  to  mankind.  The 
uses  of  iron  were  long  unknown  to  the  human  race,  the  age 
of  iron  implements  being  preceded  by  those  of  bronze  and 
stone.  Pure  metallic  iron  exists  only  in  very  small  quantity 
on  the  earth's  surface,  almost  entirely  occurring  in  those 
peculiar  structures  known  as  meteoric  stones,  which  possess 
an  extra-terrestrial  origin. 

The  process  of  obtaining  iron  from  its  ores  is  a  somewhat 
difficult  one,  and  requires  an  amount  of  knowledge  and  skill 
which  the  early  races  of  men  did  not  possess.  The  iron  of 
commerce  exists  in  three  different  forms,  exhibiting  very 
different  properties,  and  possessing  different  chemical  con 
stitutions  :  i,  wrought  ironj  2,  cast  iron;  3,  steel. 

The  first  is  nearly  pure  iron,  the  second  is  a  compound  of 
iron  with  varying  quantities  of  carbon  and  silicon,  and  the 
third  a  compound  of  iron  with  less  carbon  than  that  needed  to 
form  cast  iron.  The  modes  of  manufacture  of  these  three 
kinds  of  iron  are  essentially  different,  and  will  be  best  under 
stood  when  the  properties  of  the  metal  have  been  described. 

Pure  iron  in  the  form  of  powder  may  be  obtained  by  reduc 
ing  the  oxide,  moderately  heated  in  a  current  of  hydrogen  ;  it 
must,  however,  be  retained  in  an  atmosphere  of  hydrogen,  as 
finely-divided  iron  takes  fire  and  burns  to  oxide  when  exposed 
to  the  air.  A  button  of  pure  iron  may  be  prepared  by  expos 
ing  fine  iron  wire  mixed  with  some  oxide  of  iron  to  a  very 
high  temperature  in  a  covered  crucible,  the  oxide  retaining 
the  traces  of  impurity  which  the  wire  contained.  Iron  has  a 
bright  white  color,  and  is  remarkably  tough,  though  soft,  an 
iron  wire  two  mm.  in  thickness  not  breaking  until  when 
weighted  with  250  kilogs.  The  pure  metal  crystallizes  in 
cubes ;  iron  which  has  been  uniformly  hammered  exhibits, 
when  broken,  a  granular  and  crystalline  structure :  this 


Elementary  Chemistry.  185 

structure  becomes,  however,  fibrous  when  the  iron  is  rolled 
into  bars,  and  the  more  or  less  perfect  form  of  the  fibre  deter 
mines  to  a  great  extent  the  value  of  the  metal.  This  fibrous 
texture  of  hammered  bar  iron  undergoes  a  change  when 
exposed  to  long  continued  vibration,  the  iron  returning  to  its 
original  crystalline  condition ;  and  many  accidents  have 
occurred  in  the  sudden  snapping  of  railway  axles,  owing  to 
this  change  from  the  fibrous  to  the  granular  texture.  Wrought 
iron  melts  at  a  very  high  temperature  ;  but  as  it  becomes  soft 
at  a  much  lower  point,  it  can  be  easily  worked,  especially  as, 
when  hot,  it  possesses  the  peculiar  property  of  "  welding ; " 
that  is,  the  power  of  uniting  firmly  when  two  clean  surfaces  of 
hot  metal  are  hammered  together. 

Iron  and  certain  of  its  compounds  are  strongly  magnetic, 
but  the  metal  loses  this  power  when  red-hot,  regaining  it  upon 
cooling.  A  solid  mass  of  iron  does  not  oxidize  or  tarnish  in 
dry  air,  at  the  ordinary  temperature,  although  iron  powder 
takes  fire  spontaneously  ;  but  if  heated,  it  oxidizes  with  the 
production  of  black  scales  of  oxide,  and  when  more  strongly 
heated  in  the  air,  or  plunged  into  oxygen  gas,  it  burns  with 
the  formation  of  the  same  black  oxide.  In  pure  water,  iron 
does  not  lose  its  brilliancy ;  but  if  a  trace  of  carbonic  acid  is 
present,  and  access  of  air  is  permitted,  the  iron  begins  at  once 
to  oxidize  at  the  surface,  or  to  rust,  forming  a  hydrated  ses- 
quioxide.  Iron  decomposes  steam  at  a  red  heat,  liberating 
hydrogen  (see  p.  15),  and  forming  the  black  oxide  produced  by 
the  combustion  of  iron  in  oxygen.  The  oxides  of  iron  are 
four  in  number:  (i)  the  monoxide,  or  ferrous  oxide,  FeO, 
from  which  the  green  or  ferrous  salts  are  derived  ;  (2)  the 
sesqui  or  ferric-oxide,  Fe2O3,  yielding  the  yellow  ferric  salts  ; 
(3)  the  magnetic,  or  black  oxide,  Fe3O4,  which  does  not  form 
any  definite  salts  ;  (4)  ferric  acid,  H2FeO4,  a  weak  acid,  form 
ing  colored  salts  with  potassium. 

Ferrous  Oxide,  or  Protoxide  of  Iron,  FeO.  This  sub 
stance  has  not  been  prepared  in  the  pure  state,  owing  to  the 
great  readiness  with  which  it  absorbs  oxygen,  passing  into 
the  higher  oxides.  Hydrated  ferrous  oxide  is  thrown  down 


1 86  Elementary  Chemistry. 

as  a  white  precipitate,  when  potash  or  soda  is  added  to  a 
soluble  ferrous  salt ;  this  white  precipitate  can  only  be 
obtained  in  complete  absence  of  oxygen,  as  it  at  once  absorbs 
this  gas,  yielding  a  greenish -brown  precipitate  of  a  higher 
oxide.  This  oxide  colors  glass  green  (see  p.  1 76),  and  gives 
the  peculiar  tint  to  common  bottle-glass.  The  most  impor 
tant  of  the  ferrous  salts  are — 

Ferrous  Sulphate,  Fe  SO4  +  7  H-,O.  This  soluble  salt, 
sometimes  called  green  vitriol,  is  obtained  by  dissolving  (i) 
metallic  iron,  or  (2)  ferrous  sulphide,  in  sulphuric  acid,  or  by 
the  slow  oxidation  of  pyrites,  Fe  S2. 

(1)  Fe  +  H2SO4  =  Fe  SO4  +  H2 

(2)  FeS  +  H2SO4  =  Fe  SO4  +  H2S. 

The  solution  thus  obtained  yields  on  evaporation  large 
green  crystals  of  the  salt.  It  is  largely  used  in  the  manufac 
ture  of  several  black  dyes,  and  is  one  of  the  constituents  of 
writing-ink.  Like  ferrous  oxide,  this  salt  easily  takes  up 
oxygen,  producing  a  new  salt  called  ferric  sulphate. 

Ferrous  Chloride,  Fe  C12.  When  dry  hydrochloric  acid  gas 
is  passed  over  hot  metallic  iron,  ferrous  chloride  and  hydrogen 
are  formed  ;  the  hydrated  chloride  is  also  produced  when  iron 
is  dissolved  in  aqueous  hydrochloric  acid,  green  crystals  being 
deposited,  having  the  composition  Fe  C12  +  4  H2O. 

Ferrous  Carbonate,  Fe  COs.  This  is  an  insoluble  com 
pound,  and  occurs  largely  as  a  mineral,  constituting  the  clay 
iron-stone  ;  the  ore  of  iron  from  which  a  large  proportion  of 
our  iron  is  prepared. 

Ferrous  Sulphide,  Fe  S,  an  invaluable  compound,  formed 
by  fusing  equivalent  quantities  of  sulphur  and  iron  together,  is 
employed  in  the  laboratory  for  the  generation  of  sulphuretted 
hydrogen  (see  p.  114).  A  disulphide,  Fe  S2,  called  iron 
pyrites,  is  found  in  large  quantities,  and  is  much  used  in  the 
production  of  sulphuric  acid  (see  p.  1 1 1). 

Ferric  Oxide,  Fe3  Oa.  This  oxide  occurs  native,  as  the 
minerals  red  haematite  and  specular  iron  ore,  whilst,  combined 
with  water,  it  forms  brown  haematite.  It  may  be  readily  pre- 


Elementary  Chemistry,  187 

pared  artificially  by  heating  ferrous  sulphate  to  redness  ;  or  by 
adding  solution  of  ammonia  or  caustic  potash  to  a  solution  of 
a  ferric  salt,  when  the  hydrated  oxide  falls  down  as  a  bulky 
brownish-red  powder,  which  dissolves  in  acids,  forming  the 
ferric  salts:  thus,  when  acted  upon  by  sulphuric  *c\&,  ferric 
sulphate,  Fe2  38 O4,  is  produced  ;  and  by  hydrochloric  acid, 
ferric  chloride,  Fe2  C16.  Of  the  ferric  salts,  the  chloride  is  the 
most  important ;  the  anhydrous  salt  forms  in  brilliant  red 
crystals  when  chlorine  gas  is  passed  over  heated  metallic 
iron.  Solutions  of  the  ferric  salts  can  be  reduced  by  various 
deoxidizing  agents  to  the  corresponding  ferrous  salts,  whilst 
these  latter,  in  contact  with  an  oxidizing  agent,  pass  into  the 
ferric  salts.  The  ferrous  salts  are  distinguished  by  their  light 
green  color,  by  their  solutions  giving  (i)  a  white  precipitate, 
with  caustic  alkalies  ;  (2)  a  light  blue  precipitate,  with  potas 
sium  ferrocyanide,  which  rapidly  becomes  dark :  whilst  the 
ferric  salts  are  yellow-colored,  and  their  solutions  yield  (i)  a 
deep  reddish-brown  precipitate,  with  the  caustic  alkalies  ;  and 
(2)  a  deep  blue  precipitate,  with  potassium  ferrocyanide. 
Ferrous  oxide  and  the  ferrous  salts  are  magnetic,  whilst  the 
ferric  oxide  and  salts  are  not  magnetic. 

The  Magnetic,  or  Black  Oxide,  Fes  O-t,  occurs  native,  crys- 
tallyzed  in  cubes,  and,  as  the  mineral  loadstone,  it  constitutes 
one  of  the  most  valued  ores  of  iron.  It  is  the  oxide  formed 
when  iron  is  oxidized  at  a  high  temperature  in  the  air,  in  oxy 
gen,  or  in  aqueous  vapor.  A  corresponding  sulphide,  FesS<, 
is  also  magnetic. 

Ferric  Acid.  The  potassium  salt  of  this  acid  is  prepared 
by  fusing  ferric  oxide  and  nitre  together  ;  the  mass  yields, 
with  water,  a  purple-colored  solution,  and  contains  potas 
sium  ferrate,  K2  FeO4.  It  is  an  exceedingly  unstable  sub 
stance  ;  neither  the  acid  H2  Fe  O4,  nor  the  oxide  Fe3  O6  have 
been  prepared. 

Manufacture  of  Iron.  The  oldest  method  of  manufactur 
ing  wrought  iron  was  to  reduce  it  at  once  from  the  ore  by 
heating  in  a  wind-furnace  with  charcoal  or  coal,  and  to  ham 
mer  out  the  spongy  mass  of  iron  thus  obtained.  This  plan 


i88 


Elementary  Chemistiy. 


can  only  be  economically  employed  on  a  small  scale,  and  with 
the  purest  forms  of  iron  ore,  and  has  been  superseded  by  a 
more  complicated  method,  applicable,  however,  to  all  kinds 
of  iron  ore.  This  consists  in  the  formation  of  cast  iron  as 
the  first  product,  and  the  subsequent  separation  of  the  carbon 
and  silicon  which  the  cast  iron  contains.  Cast  iron  is  manu 
factured  in  England  chiefly  from  clay  iron-stone,  which  gen 
erally  occurs  in  masses,  situated  in  the  immediate  neighbor 
hood  of  a  coal  seam.  The  clay  iron-stone  (ferrous  carbonate, 
with  clay)  is  first  roasted,  in  which  operation  the  carbonic 
acid  is  driven  off,  and  ferric  oxide  formed,  the  ore  afterwards 
being  thrown,  together  with  coal  and  limestone,  into  a  blast 
furnace,  the  construction  of  which  is  seen  in  Fig.  56.  It  has 
the  shape  of  a  double  cone  (A  B,  Fig.  56),  built  of  strong  fire- 


FIG.  56. 

brick  and  masonry,  and  is  about  fifty  feet  in  height,  and  fif 
teen  to  eighteen  feet  in  width  at  the  broadest  part.  The 
furnace  is  closed  at  the  bottom,  the  air  necessary  for  the 
maintenance  of  the  combustion  being  supplied  in  a  powerful 
blast,  blown  through  pipes  called  tuyeres  (c),  whilst  the  mix 
ture  of  fuel  and  ore,  being  cast  in  at  the  top  of  the  furnace  (D), 


Elementary  Chemistry.  189 

is  added  continually  as  the  burning  mass  sinks  down,  and  the 
molten  mass  is  drawn  off  at  the  bottom  so  that  one  furnace 
often  does  not  stop  working  for  several  years.  At  the  lowest 
part  of  the  structure  is  the  earth  (E),  where  the  melted  metal 
and  fused  slag  collect,  the  former  being  occasionally  tapped 
from  the  bottom  of  the  earth,  and  cast  into  pigs  in  moulds 
made  in  the  sand,  whilst  the  lighter  slag,  which  swims  on  the 
surface  of  the  metal,  runs  continually  out  from  an  opening  at 
the  upper  part  of  the  hearth. 

The  first  chemical  change  which  the  roasted  iron  ore,  or 
impure  ferric  oxide,  undergoes  in  its  passage  from  the  top  to 
the  bottom  of  the  furnace,  is  its  reduction  to  a  porous  mass 
of  metallic  iron,  by  the  carbonic  oxide  gas  proceeding  from 
the  lower  layers  of  burning  coal ;  the  temperature  of  this 
portion  of  the  furnace  is,  however,  much  too  low  to  melt  the 
iron,  and  it  therefore  sinks  down  unchanged,  together  with 
the  clay  and  limestone,  until  it  reaches  a  point  at  which  the 
heat  is  greater.  Here  the  second  change  occurs  ;  viz.  the 
clay,  sand,  and  other  impurities  of  the  ore  unite  with  the 
limestone  to  form  a  fusible  silicate  or  slag,  whilst  the  heated 
metal  coming  in  contact  with  carbon,  unites  at  once  with  it  to 
form  cast  iron,  a  fusible  compound,  which  runs  down  to  the 
bottom  of  the  furnace.  This,  in  passing  through  the  hot 
test  portion  of  the  furnace,  reduces  the  silica,  with  which  it 
meets,  to  silicon,  and,  combined  with  this,  it  forms  cast  iron. 

The  properties  and  appearance  of  cast  irons  vary  much 
with  the  quantity  of  carbon  and  silicon  which  they  contain  ; 
for  cast  iron  is  not  a  definite  chemical  compound  of  these 
elements  with  iron.  The  carbon  is  found  in  cast  iron,  (i)  as 
scales  of  graphite,  giving  rise  to  mottled  cast  iron  ;  and  (2)  in 
combination,  forming  white  cast  iron.  Sometimes  sulphur 
and  phosphorus  are  also  found  in  cast  iron,  but  these  must 
be  considered  as  impurities.  A  great  saving  of  fuel  in  the 
working  of  blast  furnaces  has  lately  been  effected  by  employ 
ing  the  heat  of  combustion  of  the  waste  gases — which  usually 
escape  and  burn  at  the  top  of  the  furnace — to  raise  the  tem 
perature  of  the  blast  of  air  supplying  the  furnace. 


Elementary  Chemistry. 

In  order  to  obtain  wrought  from  cast  iron,  the  latter  must 
undergo  the  processes  of  "  refining  "  and  "  puddling."  These 
consist  essentially  in  burning  out  the  carbon,  silicon,  sulphur, 
and  phosphorus,  by  exposing  the  heated  metal  to  a  current  of 
air  in  a  reverberatory  furnace  ;  the  melted  cast  iron  becomes 
first  covered  with  a  coat  of  oxide,  and  gradually  thickens  so 
as  to  allow  of  its  being  rolled  into  large  lumps  or  balls. 
During  this  process  the  whole  of  the  carbon  escapes  as  car 
bonic  oxide,  and  the  silicon  becomes  oxidized  to  silica,  which 
unites  with  the  oxide  of  iron,  and  forms  a  fusible  slag  ;  any 
phosphorus  or  sulphur  contained  in  the  pig  iron  is  also 
oxidized  in  this  process.  The  ball  is  then  hammered  to  give 
the  metal  coherence,  and  to  squeeze  out  the  liquid  slag,  and 
the  mass  is  afterwards  rolled  into  bars  or  plates. 

Another  interesting  branch  of  the  iron  trade  is  the  manu 
facture  of  steel ;  this  useful  substance  is  formed  when  bars 
of  wrought  iron  are  heated  to  redness  for  some  time  in  con 
tact  with  charcoal :  the  bar  is  then  found  to  have  become 
fine-grained  instead  of  fibrous,  the  substance  is  more  mal 
leable  and  more  easily  fusible  than  the  original  bar  iron,  and 
is  found  to  contain  carbon  varying  in  amount  from  one  to  two 
per  cent.  Steel  possesses  several  important  properties, 
especially  the  power  of  becoming  very  hard  and  brittle  when 
quickly  cooled,  which  fits  it  for  the  preparation  of  cutting- 
tools,  &c.  ;  these  are,  however,  generally  made  of  bar-steel, 
which  has  been  previously  fused  and  cast  into  ingots. 

A  new  and  very  rapid  mode  of  preparing  cast  steel,  which 
is  both  of  high  scientific  interest  and  industrial  importance, 
is  that  known  as  the  Bessemer  process.  This  process  con 
sists  in  burning  out  all  the  carbon  and  silicon  in  cast  iron  by 
passing  a  blast  of  atmospheric  air  through  the  molten  metal, 
and  then  in  adding  such  a  quantity  of  pure  cast  iron  to  the 
wrought  iron  thus  prepared  as  is  necessary  to  give  carbon 
enough  to  convert  the  whole  mass  into  steel ;  the  melted 
steel  is  then  at  once  cast  into  ingots.  In  this  way  six  tons  of 
cast  iron  can  at  one  operation  be  converted  into  steel  in 
twenty  minutes.  The  Bessemer  steel  is  now  largely  manu- 


Elementary  Chemistry.  191 

factured  for  railway  axles  and  rails,  for  boiler-plates,  and  other 
purposes,  for  which  it  is  much  more  fitted  than  wrought  iron, 
so  that  this  process  bids  fair  to  revolutionize  the  old  iron 
industry. 


•LESSON  XXIII. 

3.  COBALT.  Symbol  Co.  Combining  Weight  587.  Spe 
cific  Gravity  8*5. 

Cobalt  is  a  reddish-white,  very  tenacious  metal,  which  is  as 
infusible  as  iron,  and,  like  the  latter  metal,  is  strongly  magnetic. 
It  is  not  found  native,  but  occurs  in  combination  with  arsenic 
and  sulphur,  as  two  distinct  minerals.  The  metal  dissolves 
slowly  in  sulphuric  and  hydrochloric  acids  with  evolution  of 
hydrogen.  The  cobalt  compounds  are  distinguished  for  the 
brilliancy  of  their  color  ;  they  are  employed  as  pigments,  and 
they  impart  a  magnificent  blue  tint  to  glass.  There  are  two 
oxides  of  cobalt,  the  monoxide,  CoO,  and  the  sesquioxide, 
Co2  O3  :  the  former,  on  solution  in  acids,  forms  the  protosalts 
of  cobalt,  which  are  pink  when  hydrated,  and  blue  when 
anhydrous  ;  whilst  the  sesquioxide  does  not  form  any  salts. 
The  monoxide,  CoO,  is  obtained  as  a  brown  powder  by  care 
fully  heating  the  rose-colored  hydrate,  precipitated  by  potash 
in  solutions  of  cobalt ;  and  the  sesquioxide,  Co2O3,  is  pre 
pared  by  adding  a  solution  of  bleaching-powder  to  a  soluble 
protosalt.  The  most  important  salts  of  cobalt  are  the 
Chloride,  Co  Clo,  obtained  by  acting  on  the  oxide,  or  on  the 
metallic  ore  with  hydrochloric  acid  ;  the  solution  yields  on 
evaporation  pink  crystals  of  the  hydrated  chloride,  or,  if 
further  heated,  blue  crystals  of  the  anhydrous  salt.  The 
cobalt,  nitrate,  and  sulphate,  are  also  soluble  salts  ;  the  latter 
is  isomorphous  with  magnesium  sulphate.  Cobalt  sulphide, 
Co  S,  is  a  black  powder,  insoluble  in  dilute  acids.  Cobalt  can 
be  easily  recognized  by  the  deep  blue  tint  which  very  minute 


192  Elementary  Chemistry. 

traces  impart  to  glass,  or  to  a  borax  bead,  made  by  fusing 
borax  into  a  colorless  mass  on  the  loop  of  a  platinum  wire. 

4.  NICKEL.    Symbol  Ni.    Combining  Weight  587.   Specific 
Gravity  8*8. 

Nickel  occurs  in  large  quantities,  combined  with  arsenic, 
as  kupfernickel;  also  together  with  cobalt  in  speissj  and  it  is 
now  prepared  in  considerable  quantities  for  the  manufacture 
of  German  silver,  an  alloy  of  nickel,  zinc,  and  copper.  Nickel 
is  a  white,  malleable  and  tenacious  metal ;  it  melts  at  a  some 
what  lower  temperature  than  iron,  and  is  strongly  magnetic, 
but  loses  this  property  when  heated  to  350°.  There  are  two 
oxides  of  nickel,  the  monoxide,  Ni  O,  and  the  sesquioxide, 
Ni3O3 :  the  former  of  these  gives  rise  to  the  nickel  salts, 
which  possess  a  peculiar  apple-green  color.  The  monoxide 
is  obtained  by  heating  the  nitrate  or  carbonate,  or  by  precipi 
tating  a  soluble  nickel  salt  with  caustic  potash,  and  heating 
the  apple-green  hydrate,  which  is  thrown  down.  The  sesqui- 
oxide  is  a  black  powder,  prepared  by  adding  a  solution  of 
bleaching-powder  to  a  soluble  nickel  salt.  The  important 
soluble  nickel  salts  are  the  sulphate,  NiSCX  +  7H2O,  crys 
tallizing  in  green  prisms  ;  Ni  2  (NO3),  the  nitrate ;  and  the 
chloride,  NiCl2.  Like  cobalt,  nickel  forms  a  black  sulphide, 
Ni  S,  insoluble  in  dilute  acids  ;  but  the  nickel  salts  may  be 
distinguished  from  those  of  the  former  metal  by  imparting  a 
reddish-yellow  color  to  the  borax  bead,  as  well  as  by  their 
green  color. 

5.  CHROMIUM.       Symbol  Cr.      Combining   Weight   52-5. 
Specific  Gravity  6'8. 

Chromium  is  a  substance  whose  compounds  do  not  occur 
very  widely  distributed,  or  in  large  quantities,  but  they  are, 
nevertheless,  much  employed  in  the  arts  as  pigments,  many 
of  them  possessing  a  fine  bright  color.  The  chief  ore  of  this 
metal  is  a  compound  of  the  oxides  of  chromium  and  iron, 
called  chrome  iron-stone,  found  in  America,  Sweden,  and  the 
Shetlands ;  a  compound  of  chromium,  lead,  and  oxygen, 


Elementary  Chemistry.  193 

called  lead  chromate,  is  also  found  in  some  quantity.  Pure 
chromium  appears  to  be  the  most  infusible  of  all  the  metals, 
as  it  cannot  be  melted  at  a  temperature  sufficient  to  fuse  and 
volatilize  platinum  ;  it  has,  however,  been  obtained  by  another 
process,  in  the  form  of  bright  crystals  belonging  to  the  cubic 
system.  Chromium  unites  with  oxygen  in  four  different  pro 
portions  :  (i)  chromous  oxide,  CrO  ;  (2)  chromic  sesquioxide, 
Cr2  O3 ;  (3)  chromo-chromic  oxide,  Cr  O  Cr2O3 ;  (4)  chrome 
trioxide,  CrO3.  The  two  first  of  these  oxides  yield  correspond 
ing  chlorides  and  salts  ;  thus,  CrO,  Cr2O3,  CrCl2,Cr2Cl8;  the 
third  oxide  is  a  neutral  body,  corresponding  to  the  magnetic 
oxide  of  iron  ;  and  the  fourth  oxide  forms  with  water  an  acid. 
Chromous  oxide,  CrO,  is  only  known  in  the  hydrated  state, 
as  both  it  and  its  compounds  absorb  oxygen  with  great 
avidity ;  the  hydrate  is  prepared  as  a  brown  precipitate  by 
adding  potash  to  the  solution  of  chromous  chloride.  Chrome 
sesquioxide,  Cr2O3,  is  a  perfectly  stable  substance,  prepared 
by  igniting  the  hydrate  precipitated  by  adding  ammonia  to  a 
solution  of  chromic  chloride.  Chrome  trioxide,  CrO3,  is  pre 
pared  by  adding  strong  sulphuric  acid  to  a  saturated  solution 
of  potassium  chromate  ;  potassium  hydric-sulphate,  water, 
and  chrome  trioxide  being  formed  :  the  latter  crystallizing  out 
in  splendid  long,  ruby-red  prisms.  Chrome  trioxide  is  a 
very  deliquescent  substance,  which  in  solution  in  water  has  a 
strong  acid  reaction,  and  may  then  be  termed  chromic  acid, 
neutralizing  bases,  and  forming  yellow  or  red-colored  salts, 
called  chromates.  Chrome  trioxide  gives  up  a  portion  of  its 
oxygen  very  readily  when  placed  in  contact  with  organic 
matter,  being  reduced  to  chrome  sesquioxide.  The  most 
ready  mode  of  preparing  a  solution  of  chromic  chloride,  Cr2Cl6, 
is  to  boil  a  solution  of  chromic  acid,  or  a  chromate  with  hydro 
chloric  acid  and  alcohol,  the  red  or  yellow  solution,  after  a  few 
minutes,  being  changed  to  a  deep  greenish-blue  color.  A 
solution  of  chromic  sulphate,  Cr23SO4,  may  be  obtained  in 
like  manner  by  substituting  sulphuric  for  hydrochloric  acid. 
This  salt  forms  a  series  of  alums  with  potassium  and  ammo 
nium  sulphate,  which  have  a  deep  purple  tint,  and  are  isomor- 

9 


194  Elementary  Chemistry. 

phous  with  common  alum.  The  anhydrous  chromic  chloride 
is  obtained  as  a  sublimate,  in  beautiful  violet  crystals,  by  pass 
ing  a  stream  of  chlorine  gas  over  a  red-hot  mixture  of  chrome 
sesquioxide  and  charcoal.  If  any  salt  of  the  chrome  sesqui- 
oxide  is  fused  with  an  alkaline  carbonate,  it  becomes  oxidized, 
and  an  alkaline  chromate  is  formed,  and  this  is  the  mode  by 
which  all  the  chromium  compounds  are  prepared  from  chrome 
iron  ore.  Three  potassium  chromates  are  known  :  (i)  neutral 
potassittm  chromate,  K3Cr  O4 ;  (2)  potassium  anhydro-chro- 
mate,  or  bichromate,  K2CrO4,CrO3  ;*  and  (3)  potassium  dian- 
hydrochr ornate,  or  terchromate,  K2CrO42CrOs.  The  first  of 
these  salts  is  deposited  in  yellow  crystals,  which  are  isomor- 
phous  with  potassium  sulphate,  when  chrome  iron-stone  is 
heated  with  caustic  potash  ;  the  second  crystallizes  in  large 
red  prisms  on  adding  to  a  solution  of  the  neutral  chromate 
sulphuric  acid  sufficient  to  combine  with  half  the  base  ;  this 
salt  is  manufactured  on  a  large  scale,  and  serves  for  the  pre 
paration  of  the  various  chrome  pigments  ;  the  third  potassium 
chromate  is  an  unimportant  salt,  obtained  by  crystallizing  the 
second  compound  with  an  excess  of  chromic  trioxide. 

The  chief  of  the  insoluble  chromates  are  lead  chromate, 
Pb  Cr  O4,  or  chrome  yellow,  obtained  by  precipitating  potas 
sium  chromate  by  a  soluble  lead  salt,  and  largely  used  for 
dyeing  and  other  purposes  in  the  arts ;  silver  chromate, 
Ag'2CrO4,  a  characteristic  deep-red  colored  precipitate ;  and 
barium  chromate,  BaCrO4,  also  a  yellow  insoluble  powder. 

A  volatile  compound  intermediate  between  chrome  trioxide 
and  chromic  chloride  is  known,  termed  chlorochromic  oxide, 
Cr  Oa  Cla  ;  this  substance  is  obtained  in  the  form  of  a  dark 
red,  strongly  fuming  liquid,  when  a  soluble  chromate  is  distilled 
with  sulphuric  acid  and  common  salt ;  the  vapor  density  of 
chlorochromic  oxide  is  777  (when  H  =  i),  the  specific  gravity 
of  the  liquid  17,  and  its  boiling  point  1 21°.  It  may  be  re 
garded  as  chrome  trioxide  in  which  one  atom  of  oxygen  has 
been  replaced  by  its  equivalent  of  chlorine,  and  is  analogous 
to  chloro-sulphuric  acid  and  to  many  organic  compounds. 

*  A  salt  analogous  to  borax  (p.  125). 


Elementary  Chemistry.  195 

The  presence  of  chromium  and  its  compounds  can  be  easily 
detected  by  the  formation  of  soluble  yellow-colored  alkaline 
salts,  yielding  insoluble  lead  and  silver  compounds,  and  ca 
pable  of  easy  reduction  to  green  solutions  in  presence  of 
organic  matter.  Chromic  oxide  imparts  to  glass  or  borax  a 
fine  deep  green  color. 

6.  URANIUM.    Symbol  U.     Combining  Weight  120.     Spe 
cific  Gravity  18*4. 

Uranium  is  a  metal  which  occurs  but  sparingly  in  nature, 
existing  combined  in  two  somewhat  rare  minerals,  pitchblende 
and  uranite.  The  metal  is  of  a  steel-white  color,  and  it  does 
not  oxidize  in  dry  air  at  ordinary  temperatures,  but  when 
strongly  heated  it  burns  brilliantly.  There  are  two  oxides 
which  form  salts,  viz.  uranous  oxide,  UO,  and  uranic  oxide, 
U2O3 ;  the  uranous  salts  are  green,  whilst  the  uranic  com 
pounds  are  yellow  ;  and  these  latter  solutions  give  yellow 
precipitates,  with  an  alkali,  in  which  the  uranic  oxide  acts  as 
an  acid,  forming  a  uranate  of  the  base.  The  sulphide  is  an 
insoluble  salt  of  a  yellowish-brown  color.  The  chief  applica 
tion  of  uranium  compounds  is  for  the  purpose  of  glass-stain 
ing  ;  the  uranous  oxide  imparts  a  fine  black,  and  the  uranic 
oxide  a  beautiful  yellow,  to  glass  ;  uranium  compounds  are 
also  now  used  in  photography. 

7.  INDIUM.     Symbol  In.     Combining  Weight  74*0 

A  metal  lately  discovered  by  means  of  spectrum  analysis  in 
certain  zinc  ores.  Its  compounds  impart  a  blue  color  to 
flame,  and  its  spectrum  is  characterised  by  a  fine  indigo- 
colored  line.  The  properties  of  indium  and  its  compounds 
have  as  yet  not  been  fully  examined,  but  in  its  general  be 
havior  it  resembles  the  metals  of  the  foregoing  group. 


CLASS  VI.     i,  TIN.    2,  TITANIUM. 

I.  TIN.     Symbol  Sn.  (Stannum).     Combining  Weight  1 18. 
Specific  Gravity  7-3. 


196  Elementary  Chemistry. 

The  ores  of  tin — although  this  metal  has  been  known  from 
very  early  times — occur  in  but  few  localities,  and  the  metallic 
tin  is  not  found  in  nature.  The  chief  European  sources  of 
tin  are  the  Cornish  mines,  where  it  is  found  as  tin  dioxide  or 
tin-stone.  It  is  in  all  probability  from  these  mines  that  the 
Phoenicians  and  Romans  obtained  all  the  tin  which  they  em 
ployed  in  the  manufacture  of  bronze.  Tin-stone  is  also  met 
with  in  Malacca,  and  Borneo,  and  Mexico.  In  order  to  pre 
pare  the  metal,  the  tin-stone  is  crushed  and  washed  to  remove 
mechanically  the  lighter  portions  of  rock  with  which  it  is 
mixed,  and  the  purified  ore  is  then  placed  in  a  reverberatory 
furnace  with  anthracite  or  charcoal  and  a  small  quantity  of 
lime  ;  the  oxide  is  thus  reduced,  and  the  liquid  metal,  to 
gether  with  the  slag,  consisting  of  silicate  of  lime,  falls  to  the 
lower  part  of  the  furnace.  The  blocks  of  tin,  still  impure,  are 
then  refined  by  gradually  melting  out  the  pure  tin,  leaving  an 
impure  alloy  behind.  English  tin  generally  contains  traces 
of  arsenic,  copper,  and  other  metals  ;  that  imported  from 
Banca  is  nearly  chemically  pure. 

Tin  possesses  a  white  color  resembling  that  of  silver  ;  it  is 
soft,  malleable  and  ductile,  but  possesses  little  tenacity,  a  wire 
two  mms.  in  diameter  breaking  with  a  weight  of  sixteen  kilos. 
When  bent,  pure  tin  emits  a  peculiar  crackling  sound  ;  tin 
melts  at  235°,  and  is  not  sensibly  volatile.  Tin  does  not  lose 
its  lustre  on  exposure  to  the  air,  whether  dry  or  moist,  at  or 
dinary  temperature,  but  if  strongly  heated  it  takes  fire,  and  a 
white  powder  of  stannic  oxide  (sometimes  termed  putty 
powder)  is  formed.  Hydrochloric  acid  dissolves  tin  with  the 
evolution  of  hydrogen  and  the  formation  of  stannous  chlo 
ride  ;  nitric  acid  also  attacks  the  metal  with  great  energy, 
nitrous  fumes  being  given  off  and  stannic  oxide  being  left 
as  a  white  powder.  There  are  two  well-marked  oxides  of  tin. 

Stannous  oxide,  Sn  O.  This  is  a  black  powder  prepared 
by  heating  the  stannous  hydrate  in  an  atmosphere  of  carbonic 
-acid  ;  it  rapidly  absorbs  oxygen  from  the  air,  passing  into 
stannic  oxide.  The  hydrate  falls  as  a  white  powder  when  a 
solution  of  a  stannous  salt  is  added  to  an  alkaline  carbonate. 


Elementary  Chemistry.  197 

The  stannous  chloride,  SnCl2,  is  obtained  by  dissolving  tin  in 
hydrochloric  acid,  and  separates  out  in  needle-shaped  crystals, 
SnCl2  +  2H2O,  when  the  solution  is  concentrated.  Stannous 
chloride  is  termed  "  tin  salts  "  in  commerce  ;  it  is  largely  manu 
factured  for  the  calico  printer  and  dyer,  who  use  it  as  a 
"  mordant." 

Stannic  oxide,  Sn  O2,  occurs  native  as  tin-stone,  and  it  can 
be  prepared  artificially  in  two  conditions,  possessing  totally 
different  properties.  If  tin  be  oxidized  by  nitric  acid,  stannic 
oxide  is  produced  as  a  white  powder  insoluble  in  acids  ;  if, 
on  the  other  hand,  to  a  solution  of  stannic  chloride  an  alkali 
be  added,  a  white  precipitate  is  formed  of  stannic  oxide,  which 
is  readily  soluble  in  acids.  Both  of  these  varieties  of  hydrated 
stannic  oxide  form  salts,  the  insoluble  compound  having 
been  termed  metastannic,  and  the  soluble  compound  stannic 
acid.  Sodium  stannate,  Na2  Sn  O3,  4  H2  O,  formed  by  boil 
ing  stannic  oxide  with  soda,  is  largely  used  in  calico  printing 
as  a  mordant,  and  then  termed  "  tin  prepare  liquor"  Stannic 
chloride,  Sn  C14,  is  obtained  by  passing  chlorine  gas  over 
metallic  tin;  it  is  a  colorless  liquid,  boiling  at  i2o°C,  and 
having  a  vapor  density  of  9*2.  It  fumes  strongly  in  the  air, 
and  forms  a  crystalline  hydrate,  when  a  small  quantity  of  water 
is  added,  which  easily  dissolves  in  an  excess.  Stannic  chloride 
is  also  used  by  dyers,  and  is  prepared  for  this  purpose  by 
dissolving  tin  in  cold  nitro-hydrochloric  acid.  Of  the  sulphides 
of  tin,  SnS,  stannous  sulphide,  and  Sn  S2,  stannic  sulphide, 
are  the  most  important ;  the  former  is  blackish-gray,  and  the 
latter  a  bright  yellow  crystalline  powder  known  as  mosaic 
gold,  soluble  in  alkaline  sulphides. 

Tin  can  easily  be  distinguished  in  solution  by  the  formation 
of  a  splendid  purple  color  called  purple  of  cassius,  formed 
when  gold  chloride  is  added  to  a  dilute  solution  of  stannous 
chloride.  Tin  is  also  easily  reduced  before  the  blowpipe  in 
the  form  of  white  malleable  beads.  Tin  is  largely  used  in 
the  arts  for  covering  and  thus  protecting  iron  plates,  or  for  "  tin- 
plating,"  and  also  for  preparing  several  valuable  alloys,  as  pew 
ter,  Britannia  metal,  plumbers'  solder,  bronze,  bell-metal,  &c. 


198  Elementary  Chemistry. 

2.  TITANIUM.     Symbol  Ti.     Combining  Weight  50. 

Titanium  is  a  rare  metal,  resembiing  tin  in  its  chemical 
properties.  It  is  found  in  combination  with  iron  in  the 
mineral  rutile.  The  oxides  of  titanium  correspond  to  those 
of  tin ;  viz.,  titanous  and  titanic  oxides,  Ti  O,  and  Ti  O3. 
Titanium  and  its  compounds  are  not  used  in  the  arts. 

NIOBIUM  and  TANTALUM  are  two  extremely  rare  metals, 
whose  properties  are  as  yet  but  imperfectly  known. 

CLASS  VII.    TUNGSTEN  CLASS. 

1.  MOLYBDENUM.     Symbol  Mo.     Combining  Weight  96. 
The  chief  ore  of  this  metal  is  molybdic  disulphide,  a  mineral 

in  appearance  resembling  graphite.  The  metal  is  a  gray 
substance,  which  oxidizes  on  heating  in  the  air  to  molybdic 
trioxide,  Mo  Oa,  a  yellow  powder  which  acts  as  an  acid,  form 
ing  with  bases  salts  called  molybdates.  The  compounds  of 
molybdenum  do  not  occur  frequently,  and  are  not  used  in  the 
arts. 

2.  VANADIUM.     Symbol 'V.     Combining  Weight  137. 
This  is  a  very  rare  metal,  its  compounds  occur  in  small 

quantity  in  certain  iron  ores,  and  also  in  combination  as 
vanadiate  of  lead.  It  forms  an  interesting  oxide,  termed 
Vanadic  Trioxide,  V  Oa. 

3.  TUNGSTEN.       Symbol  W.      (Wolf rani}.      Combining 
Weight  184. 

This  metal  occurs  in  tolerably  large  quantities  combined 
with  ferrous  oxide  in  the  mineral  wolfram,  and  also  with  lime 
as  scheelite.  The  metal  has  only  been  obtained  as  a  grayish- 
black  powder,  having  a  specific  gravity  of  17-4.  Tungsten 
is  employed  occasionally  in  the  arts — the  addition  of  a  small 
quantity  imparts  a  great  degree  of  hardness  and  other  valuable 
qualities  to  steel.  Two  oxides  of  tungsten  are  known, — 
Tungstic  Dioxide,  W  O2,  and  Tungstic  Trioxide,  WO3.  The 
former  of  these  is  obtained  as  a  brown  powder  by  heating  the 


Elementary  Chemistry.  199 

trioxide  in  an  atmosphere  of  hydrogen  ;  the  latter,  sometimes 
called  tungstic  acid,  is  obtained  as  an  insoluble  yellow  powder 
by  heating  the  native  calciqm  tungstate  with  nitric  acid. 
Tungsten  trioxide  forms  a  variety  of  somewhat  complicated 
salts.  The  sodium  compound  is  soluble,  and  has  been  used 
to  add  to  the  starch  employed  to  stiffen  light  fabrics,  the 
tungstate  rendering  the  fabric  uninflammable. 


LESSON  XXIV. 
CLASS  VIII. — i,  ARSENIC.    2,  ANTIMONY.    3,  BISMUTH. 

1.  ARSENIC.      The  properties  of  this  element  and  its  com 
pounds  have  been  already  considered  (see  p.  133). 

2.  ANTIMONY.     Symbol  Sb  (Stibium).    Combining  Weight 
122.     Specific  Gravity  671. 

Metallic  antimony  occurs  native,  but  its  chief  ore  is  the  tri- 
sulphide.  The  metal  is  easily  reduced  by  heating  the  sul 
phide  with  about  half  its  weight  of  metallic  iron,  when  ferrous 
sulphide  and  metallic  antimony  are  formed.  Antimony  may 
also  be  reduced  by  mixing  the  ore  with  coal  and  heating  in  a 
reverberatory  furnace.  Antimony  is  a  bright  bluish-white 
colored  metal,  crystallizing  in  rhombohedra,  isomorphous  with 
arsenic.  It  is  very  brittle,  and  can  be  powdered  in  a  mortar  ; 
it  melts  at  450°,  and  may  be  distilled  at  a  white  heat  in  an 
atmosphere  of  hydrogen.  Antimony  undergoes  no  alteration 
in  the  air  at  ordinary  temperatures,  but  rapidly  oxidizes  if 
exposed  to  air  when  melted,  and,  if  heated  more  strongly,  it 
takes  fire  and  burns  with  a  white  flame,  giving  off  dense  white 
fumes  of  antimonic  trioxide.  Antimony  is  not  attacked  either 
by  dilute  hydrochloric  or  sulphuric  acids  ;  nitric  acid  attacks 
the  metal,  converting  it  into  white  insoluble  antimonic  oxide. 
Nitro-hydrochloric  acid  dissolves  antimony  easily.  The  alloys 


2OO  Elementary  Chemistry. 

of  antimony  are  largely  used  in  the  arts  ;  of  these,  type  metal 
(an  alloy  of  lead  and  antimony)  is  the  most  important :  it  con 
tains  17  to  20  per  cent,  of  the  latter  metal.  The  two  impor 
tant  oxides  of  antimony,  (i)  antimonious  oxide,  or  trioxide, 
Sba  O3,  (2)  antimonic  oxide,  Sb2  O5  (sometimes  called  anti- 
monic  acid),  correspond  to  those  of  arsenic  (see  p.  133).  A 
third  oxide  exists  unknown  in  the  arsenic  series  :  this  is  an 
intermediate  gray  oxide,  having  the  composition  Sb2  O3  Sba 
06. 

Antimonious  Oxide,  Sb2  O3.  This  oxide  gives  rise  to  the 
important  series  of  salts  of  antimony  used  in  medicine  ;  it  is 
obtained  in  crystalline  needles,  which  are  isomorphous  with 
the  rare  form  of  arsenious  oxide  (see  p.  134).  Antimonious 
oxide  has  also  been  observed  to  crystallize  in  octohedra  ; 
hence  these  two  oxides  are  said  to  be  isodimorphous.  The 
best  mode  of  preparing  the  pure  oxide  is  by  decomposing 
antimonic  chloride  with  an  alkaline  carbonate,  when  the  oxide 
is  precipitated  as  a  white  powder :  thus,  2  Sb  C13  +  3  Na2 
CO3  =  Sb2  O3  +  6  Na  Cl  +  3  CO2.  Antimonious  oxide  dis 
solves,  when  boiled  with  a  solution  of  cream  of  tartar  (hydric 
potassium  tartrate),  and  on  concentration  the  solution  deposits 
crystals  of  tartar  emetic  (potassium  antimony  tartrate) ;  anti 
monious  oxide  also  dissolves  in  hydrochloric  acid,  yielding  a 
solution  of  the  trichloride,  but  this  is  rendered  turbid  by  addi 
tion  of  water. 

Antimonic  Oxide,  Sba  Os  (sometimes  called  Antimonic 
Acid),  obtained  by  acting  on  antimony  with  strong  nitric  acid, 
or  by  decomposing  the  penta-chloride  of  antimony  with  water. 
It  is  a  light  straw-colored  powder,  which  loses  oxygen  at  a 
red  heat,  and  is  converted  into  the  intermediate  oxide  Sba 
O3  Sb2  O5.  Antimonic  oxide  forms  salts  with  the  alkalies 
called  Antimoniates,  from  which  antimonic  acid,  Sb2  Oo  H2, 
can  be  separated  as  a  white  powder.  The  oxides  prepared  by 
the  two  methods  above  given  are  found  to  possess  different 
properties  as  regards  their  power  of  uniting  with  bases.  That 
prepared  with  nitric  acid  yields  monobasic  salts,  whilst  that 
obtained  from  the  penta-chloride  yields  dibasic  salts ;  to  the 


Elementary  Chemistry.  20 1 

first  class  of  salts  the  name  Antimoniates,  and  to  the  second 
that  of  Metantimoniates  has  been  given.  The  gray  interme 
diate  oxide,  Sb2  O3  Sb2  O6,  is  obtained  by  heating  the  metal 
in  the  air  until  no  further  change  occurs. 

Finely-powdered  metallic  antimony  takes  fire  spontaneously 
when  thrown  into  chlorine  gas  with  formation  of  the  chlorides. 
There  are  two  chlorides  of  antimony  ;  antimony  tri-chloride, 
Sb  Cls,  is  obtained  as  a  buttery  mass  by  passing  chlorine  gas 
over  an  excess  of  metallic  antimony,  or  by  dissolving  the 
metal  or  sulphide  in  hydrochloric  acid  to  which  a  little  nitric 
has  been  added :  on  distilling  the  liquid  thus  obtained  the 
trichloride  volatilizes,  and,  on  cooling,  solidifies  to  a  mass  of 
white  crystals.  T\iz.penta- chloride,  Sb  C15,  is  a  mobile  strongly- 
fuming  liquid,  obtained  by  passing  an  excess  of  chlorine  over 
the  trichoride  or  the  metal.  The  sulphides  of  antimony,  Sba 
Sa,  and  Sb2  S6,  correspond  to  the  oxides,  and,  like  the  oxides, 
are  capable  of  uniting  with  the  alkaline  sulphides  to  form 
a  class  of  soluble  salts. 

Like  arsenic,  antimony  unites  with  hydrogen  to  form  a  gas 
eous  compound,  antimoniuretted  hydrogen,  Sb  Ha,  analogous 
to  As  Ha,  arseniuretted  hydrogen.  This  gas  is  evolved, 
together  with  hydrogen,  when  an  antimony  salt  is  brought  in 
contact  with  zinc  and  dilute  acid.  Like  the  corresponding 
arsenic  compound,  it  burns  with  a  bluish  flame,  evolving  a 
white-colored  antimonious  oxide,  and  is  decomposed  at  a  red 
heat  with  deposition  of  metallic  antimony.  The  detection  and 
separation  of  arsenic  and  antimony  is  a  subject  of  much  impor 
tance  in  medical  jurisprudence,  as  both  substances  exhibit 
poisonous  characters,  and  closely  resemble  one  another  in 
their  reactions  ;  still,  with  care  it  is  easy  to  discriminate 
between  these  two  metals,  and  to  detect  with  certainty  a  very 
minute  quantity  of  either  when  present  in  the  body  of  an 
animal. 

3.  BISMUTH.  Symbol Bi.  Combining  Weight  210.  Specific 
Gravity  9*8. 

This  metal  is  found  in  small  quantities  in  the  native  state, 
9* 


2O2  Elementary  Chemistry. 

but  occurs  more  often  as  a  sulphide  ;  it  is  easily  reduced  to 
the  metallic  state,  and  then  exhibits  a  pinkish-white  color.  It 
crystallizes  in  large  rhombohedra  which  can  scarcely  be  dis 
tinguished  from  cubes  ;  it  melts  at  264°,  and  is  volatilized  at 
a  white  heat.  Bismuth  does  not  oxidize  in  dry  air  at  the 
ordinary  temperature,  but  if  heated  strongly  it  burns  with  a 
blue  flame,  forming  an  oxide  ;  it  also  takes  fire  when  thrown 
into  chlorine  gas.  Bismuth  dissolves  easily  in  nitric  acid. 
The  metal  is  chiefly  used  as  an  ingredient  of  fusible  metal ; 
its  compounds  are  also  used  in  medicine,  and  as  pigments. 
Two  oxides  of  bismuth  are  known,  bis7nuthous  oxide,  Bi2O3, 
and  bismuthic  oxide,  Bi2  O6.  The  first  of  these  is  a  pale  yel 
low  powder,  for-med  when  the  metal  is  roasted  in  the  air  ;  the 
second  oxide  is  obtained  by  dissolving  the  first  in  potash  and 
precipitating  the  bismuthic  oxide  by  nitric  acid  and  heating  : 
it  is  a  reddish-brown  powder.  Like  the  corresponding  anti 
mony  compound,  bismuthic  oxide  forms  with  the  alkalies  solu 
ble  salts.  The  nitrate,  Bi  3  NO3  5H2  O,  is  the  most  impor 
tant  soluble  salt  of  bismuth ;  the  sulphide,  Bi2S3,  is  a  black 
insoluble  compound ;  the  trichloride,  BiCl3,  is  obtained  by 
heating  the  metal  in  chlorine.  One  of  the  most  striking  pecu 
liarities  of  the  bismuth  compounds  is,  that  solutions  of  the 
salts  become  milky  on  the  addition  of  water,  owing  to  the  for 
mation  of  insoluble  basic  compounds.  Metallic  bismuth  is 
easily  reduced  from  its  compounds,  before  the  blowpipe,  as  a 
brittle  bead. 

CLASS  IX.— LEAD  CLASS,     i,  LEAD.    2,  THALLIUM. 

i.  LEAD.  Symbol  Pb  {plumbum}.  Combining  Weight 
207.  Specific  Gravity  11-3. 

Lead  does  not  occur  free  in  nature ;  all  the  lead  of  com 
merce  is  obtained  from  galena,  or  lead  sulphide.  The  mode 
of  reducing  lead  from  this  ore  is  a  very  simple  one  :  the  galena 
is  roasted  in  a  reverberatory  furnace  with  the  addition  of  a 
small  quantity  of  lime  to  form  a  fusible  slag  with  any  silicious 
mineral  matter  present  in  the  ore.  By  the  action  of  the  air  a 
portion  of  the  sulphide  is  oxidized  to  sulphate,  whilst  in 


Elementary  Chemistry.  203 

another  portion  the  sulphur  burns  off  as  sulphuric  dioxide, 
and  lead  oxide  is  left  behind  ;  after  the  lapse  of  a  certain  time 
the  air  is  excluded  and  the  heat  of  the  furnace  raised — the 
lead  sulphate  and  oxide  formed  both  decompose  the  remain 
ing  sulphide,  giving  off  sulphuric  dioxide  and  leaving  metallic 
lead  behind,  thus  : 

(1)  Pb  SO4  +  Pb  S  =  2  Pb  +  2  SO2. 

(2)  2  Pb  O  +  Pb  S  =  3  Pb  +  SO2. 

Galena  almost  always  contains  small  quantities  of  silver, 
which  is  extracted  by  a  process  described  on  p.  213.  Lead 
is  a  bluish-white-colored  metal,  and  so  soft  that  it  may  be 
scratched  with  the  nail ;  it  may  be  drawn  out  to  wire,  or  ham 
mered  into  plate,  but  possesses  little  tenacity  or  elasticity, 
and  a  wire  2  mms.  in  diameter  breaks  with  a  load  of  2  kilos. 
Lead  melts  at  334°,  and  at  a  higher  temperature  volatilizes, 
though  not  in  quantity  sufficient  to  enable  it  to  be  distilled. 

The  bright  surface  of  the  metal  remains  permanently  in  dry 
air,  but  it  soon  becomes  tarnished  in  moist  air,  owing  to  the 
formation  of  a  film  of  oxide  ;  and  this  oxidation  proceeds 
rapidly  in  presence  of  a  small  quantity  of  weak  acid  such  as 
carbonic  or  acetic.  In  pure  water  freed  from  air  lead  also  pre 
serves  its  lustre,  but  if  air  be  present  lead-oxide  is  formed, 
and  this  dissolving  slightly  in  the  water  a  fresh  portion  of 
metal  is  exposed  for  oxidation.  This  solvent  action  of  water 
upon  lead  is  a  matter  of  much  importance,  owing  to  the  com 
mon  use  of  lead  water-pipes,  and  the  peculiarly  poisonous 
action  of  lead  compounds  upon  the  system  when  taken  even 
in  minute  quantities  for  a  length  of  time.  The  small  quantity 
of  certain  salts  contained  in  all  spring  and  river  waters  exerts 
an  important  influence  on  the  action  of  lead  ;  thus  waters 
containing  nitrates  or  chlorides  are  liable  to  contamination 
with  lead,  whilst  those  hard  waters  containing  sulphates  or 
carbonates  may  generally  be  brought  into  contact  with  lead 
without  danger,  as  a  thin  deposit  of  sulphate  or  carbonate  is 
formed,  which  preserves  the  metal  from  further  action.  If 
the  water  contains  much  free  carbonic  acid  it  should  not  be 


2O4  Elementary  Chemistry. 

allowed  to  come  into  contact  with  lead,  as  the  carbonate  dis 
solves  in  water  containing  this  substance.  The  presence  of 
lead  in  water  may  easily  be  demonstrated  by  passing  a  cur 
rent  of  sulphuretted  hydrogen  through  a  deep  column  of  the 
acidified  water,  and  noticing  whether  the  liquid  becomes 
tinged  of  a  brown  color,  owing  to  the  formation  of  lead  sul 
phide.  Three  compounds  of  lead  and  oxygen  are  known. 

i.  Litharge,  or  Lead  Monoxide,  Pb  O,  a  straw-colored  pow 
der,  obtained  by  heating  lead  in  a  current  of  air  ;  it  fuses  at  a 
red  heat,  forming  scaly  crystals  termed  Litharge.  Lead 
oxide  is  soluble  in  caustic  potash,  and  is  deposited  from  a  hot 
solution  in  the  form  of  rhombic  prisms.  This  oxide  forms 
with  acids  the  important  series  of  lead  salts,  which  are  gene 
rally  colorless,  and  of  which  the  soluble  ones  act  as  violent 
poisons.  Lead  oxide  combines  with  silica  to  form  an  easily 
fusible  silicate,  or  glass  ;  thus  earthen  crucibles  in  which  the 
oxide  is  fused  are  rapidly  attacked.  A  white  hydrated  oxide 
is  obtained  by  precipitating  a  soluble  salt  of  lead  by  caustic 
potash,  and  this  if  heated  yields  the  oxide.  2.  Lead  Dioxide, 
or  puce-colored  oxide,  Pb  Oa.  This  oxide  is  a  brown  powder 
obtained  by  passing  chlorine  through  the  hydrated  oxide,  or 
by  digesting  red  lead  with  nitric  acid.  Lead  dioxide  does  not 
form  salts  with  acids.  When  heated  it  yields  half  its  oxygen, 
and  acted  upon  with  warm  hydrochloric  acid,  chlorine  is 
evolved,  and  lead  chloride  is  formed. 

3.  Red  Oxide,  or  Red  Lead,  a  compound  of  the  two  last 
oxides,  having  the  composition  2  Pb  O  Pb  O2.  It  is  obtained 
by  exposing  massicot  to  the  air  at  a  moderate  red  heat,  oxy 
gen  being  absorbed.  Red  lead  is  chiefly  used  in  glass-making 
(see  p.  176).  When  treated  with  dilute  nitric  acid  the  lead 
oxide  dissolves,  forming  soluble  lead  nitrate,  leaving  the  puce- 
colored  oxide  behind. 

Of  the  soluble  salts  of  lead  the  nitrate,  Pb  2NOS,  is  the 
most  important.  This  compound  is  obtained  by  dissolving 
the  oxide,  the  carbonate,  or  metallic  lead  in  warm  nitric  acid  ; 
it  crystallizes  in  octohedra,  and  dissolves  in  eight  parts  of 
cold  water,  and  when  heated  strongly  it  yields  red  fumes  of 


Elementary  Chemistry.  205 

N  O2  (see  p.  61).  Lead  acetate,  or  sugar  of  lead,  is  also  a 
soluble  salt,  which  will  be  described  under  Acetic  Acid.  Al 
most  all  the  other  lead  salts  are  insoluble  in  water.  Lead 
Carbonate,  or  White  Lead,  Pb  CO3,  is  a  substance  much  used 
in  the  arts  as  a  paint,  and  manufactured  on  a  large  scale. 
The  salt  may  be  obtained  in  the  pure  state  by  precipitating  a 
cold  solution  of  the  nitrate  with  an  alkaline  carbonate,  when 
it  falls  down  as  a  white  powder.  For  preparing  the  salt  in 
quantity  two  plans  are  employed— the  one  similar  in  principle 
to  that  described  for  the  pure  salt ;  and  the  second  an  old 
and  interesting  process,  known  as  the  Dutch  method.  In  this 
process  thin  sheets  of  lead  are  rolled  into  a  coil,  and  each 
coil  placed  in  an  earthen  pot  containing  a  small  quantity  of 
crude  vinegar  (acetic  acid)  ;  several  hundred  of  these  jars  and 
coils  are  packed  on  a  floor  in  a  bed  of  stable  manure  or  spent 
tanbark,  and  then  covered  with  boards,  whilst  a  second  layer 
of  pots  similarly  charged  is  placed  above,  and  this  is  con 
tinued  until  the  building  is  filled.  After  remaining  thus  for 
several  weeks,  the  coils  are  taken  out,  when  the  greater  part 
of  the  lead  is  found  to  be  converted  into  white  carbonate.  It 
appears  that,  to  begin  with,  a  lead  acetate  is  formed,  and  that 
the  acetic  acid  is  gradually  driven  out  from  its  combination 
by  the  carbonic  acid  evolved  from  the  putrefying  organic 
matter,  and  thus  enabled  to  unite  with  another  portion  of  the 
lead  lying  underneath  that  which  was  first  attacked. 

Lead  sulphide,  or  galena,  Pb  S,  is  found  native,  and  consti 
tutes  the  chief  ore  of  the  metal.  It  is  prepared  as  a  black 
precipitate  by  passing  sulphuretted  hydrogen  gas  through  a 
solution  of  a  lead  salt.  Galena  crystallizes  in  cubes  and  oc- 
tohedra,  and  possesses  a  bright  bluish-white  metallic  lustre  ; 
lead  sulphate,  Pb  SO4,  is  a  white  insoluble  salt,  which  is 
found  native,  and  is  prepared  artificially  by  adding  sulphuric 
acid  to  a  soluble  lead  salt ;  lead  chloride,  PbCl2,  prepared  by 
adding  hydrochloric  acid  to  a  strong  solution  of  lead  nitrate, 
when  a  crystalline  precipitate  of  lead  chloride  is  formed.  It 
dissolves  in  about  thirty  parts  of  boiling  water,  separating 
out  in  shining  needles  on  cooling  ;  lead  iodide  is  precipitated 


206  Elementary  Chemistry. 

in  the  form  of  splendid  yellow  spangles,  when  hot  solutions 
of  potassium  iodide  and  lead  nitrate  are  mixed  and  allowed 
to  cool ;  lead  chromate  is  a  yellow  insoluble  salt.  Lead  can 
easily  be  recognized, — ist,  by  the  black  sulphide,  soluble  in 
dilute  nitric  acid  ;  2dly,  by  the  white  insoluble  sulphate  ;  3dly, 
by  the  yellow  iodide  and  chromate  ;  and  4thly,  by  the  easy 
reduction  of  the  metal  in  the  form  of  a  malleable  bead 
when  any  of  the  salts  are  heated  before  the  blowpipe  with  a 
reducing  agent. 

2.  THALLIUM.  Symbol  Tl.  Combining  Weight  204.  Spe 
cific  Gravity  ir85. 

Thallium  was  discovered  in  1861  by  Mr.  Crookes,  by  means 
of  spectrum  analysis,  in  the  deposit  in  the  flue  of  a  pyrites 
burner  (see  p.  1 10).  The  presence  of  this  new  metal  is  indi 
cated  by  the  occurrence  of  a  splendid  green  line  in  the  spec 
trum.  Metallic  thallium  closely  resembles  lead  in  its  physical 
properties  ;  the  freshly  cut  surface  has  a  bluish-white  lustre, 
which  rapidly  tarnishes  ;  it  is  so  soft  that  it  receives  impres 
sions  of  the  nail,  and  can  be  easily  drawn  into  wire  ;  it  melts 
below  a  red  heat.  It  is  found  to  occur  in  many  specimens  of 
iron  pyrites,  and  appears  to  take  the  place  of  arsenic,  which 
is  a  common  impurity  of  this  mineral.  Metallic  thallium 
undergoes  gradual  oxidation,  so  that  it  is  best  preserved  in 
water  ;  when  strongly  heated  in  oxygen,  it  takes  fire,  and 
burns  with  a  bright  green  flame.  Thallium  dissolves  easily  in 
nitric  and  sulphuric  acids  with  evolution  of  hydrogen,  but 
more  slowly  in  hydrochloric  acid,  owing  to  the  insolubility 
of  the  chloride.  Two  oxides  of  this  metal  are  well  charac 
terized,  Thallous  oxide,  T12  O,  and  Thallic  sesqui-oxide, 
T12  Oa.  Thallous  oxide  corresponds  in  composition,  and 
somewhat  resembles  in  properties,  the  alkali  potash,  K2O,  as 
it  is  soluble  in  water,  yielding  an  alkaline  caustic  solution, 
which  absorbs  carbonic  acid  from  the  air,  and  forming  a  well- 
defined  series  of  salts.  Of  these  the  sulphate,  T12SO4,  and 
the  chloride,  Tl  Cl,  are  the  most  important.  The  sulphate  is 
a  soluble  salt,  crystallizing  in  six-sided  prisms,  and  furnishing 


Elementary  Chemistry.  207 

octohedral  crystals  of  an  alum  with  aluminium  sulphate ; 
whilst  the  chloride  is  only  slightly  soluble  in  water,  in  this 
respect  more  nearly  resembling  the  corresponding  lead  salt. 
Thallium  carbonate  is  also  a  soluble  salt,  requiring  about 
twenty-five  parts  of  cold  water  for  solution.  The  sulphide, 
T12S,  is  an  insoluble  black  powder,  precipitated  when  an  al 
kaline  sulphide  is  added  to  any  soluble  thallium  compound. 
The  soluble  thallium  salts  are  colorless,  and  act  as  strong 
poisons.  The  metal  is  precipitated  in  a  pulverulent  form, 
when  a  piece  of  zinc  is  introduced  into  its  solutions.  It  will 
be  seen  that  the  properties  of  thallium  are  intermediate 
between  those  of  lead  and  the  alkalies.  Thallium  is  mona- 
tomic,  204  parts  of  this  metal  replacing  one  part  of  hydrogen. 


LESSON  XXV. 

CLASS   X.     SILVER   CLASS,      i,  COPPER.     2,   MERCURY. 
3,  SILVER. 

i.. COPPER.  Symbol  Cu.  Combining  Weight  63-5.  Specific 
Gravity  8-93. 

Copper  is  an  important  metal,  largely  used  in  the  arts,  and 
has  been  known  from  very  early  times,  as  it  occurs  native  in 
the  metallic  state,  and  is  moreover  easily  reduced  from  its 
ores.  Metallic  copper  is  found  in  considerable  quantity  in 
North  America  and  other  localities,  crystallizing  in  cubic  and 
octohedral  forms,  but  the  chief  sources  of  copper  are  the  fol 
lowing  ores :  (i)  A  compound  of  copper,  sulphur,  and  iron, 
known  as  copper  pyrites,  Cu,S  +  Fe2  S3.  (2)  The  cuprous 
sulphide,  Cu2  S.  (3)  The  carbonate  or  malachite  ;  and  (4) 
The  red  or  cuprous  oxide,  Cu2  O.  The  Cornish  mines  yield 
large  quantities  of  copper,  whilst  much  ore  is  furnished  by 
Chili  and  South  Australia.  Pure  metallic  copper  can  be 
obtained  by  reducing  the  oxide  in  a  current  of  hydrogen  gas, 


208  Elementary  Chemistry. 

or  by  the  electrolytic  decomposition  of  a  salt  of  copper.  The 
process  for  obtaining  copper  on  a  large  scale  from  the  carbo 
nate  or  oxide  is  a  very  simple  one,  viz..  merely  reducing  these 
ores  together  with  carbon  and  some  silica  in  a  wind  furnace. 
The  reduction  of  the  metal  is  more  difficult  when  the  com 
moner  ore,  copper  pyrites,  is  employed.  In  this  case  the  ore 
is  repeatedly  roasted,  in  order  partially  to  convert  the  cuprous 
sulphide  into  oxide,  and  the  roasted  ore  melted  in  a  rever- 
beratory  furnace  with  the  addition  of  sand  or  silicious  slag ; 
in  this  operation  the  cuprous  oxide  becomes  converted  into 
the  corresponding  sulphide,  whilst  the  iron  oxidizes  and  unites 
with  the  silica  to  form  a  light  and  fusible  slag.  The  impure 
cuprous  sulphide  fuses  and  sinks  to  the  lower  portion  of  the 
furnace,  forming  the  "  mat "  or  coarse  metal ;  and  by  repeat 
ing  this  operation,  a  pure  cuprous  sulphide  or  "  fine  metal "  is 
obtained.  In  order  to  prepare  the  metallic  copper  free  from 
sulphur,  this  fine  metal  is  roasted,  and  afterwards  fused  in 
contact  with  the  air.  During  the  first  part  of  the  operation  a 
portion  of  the  sulphur  is  burnt  off,  cupric  oxide  being  formed, 
and  in  the  later  stages  of  the  process  this  oxide  acts  upon  the 
remaining  quantity  of  sulphide,  forming  sulphuric  dioxide,  and 
metallic  copper,  Cu2  S  +  2  Cu  O  =  SO2  +  4  Cu.  In  order 
to  get  rid  of  the  last  traces  of  oxide,  the  molten  copper  is 
"poled"  or  stirred  up  with  a  piece  of  green  wood. 

Metallic  copper  possesses  a  peculiar  deep  red  color,  which 
is  best  seen  when  a  ray  of  light  is  several  times  reflected  from 
a  bright  surface  of  the  metal ;  it  is  very  malleable  and  ductile, 
and  possesses  great  tenacity,  a  wire  of  two  mms.  in  diameter 
supporting  a  weight  of  140  kilos.  ;  it  melts  at  a  red  heat,  and 
is  slightly  volatile  at  a  white  heat,  communicating  a  green  tint 
to  a  flame  of  hydrogen  gas,  which  is  passed  over  it,  and  it  is 
one  of  the  best  conductors  of  heat  and  electricity.  Copper 
does  not  oxidize  either  in  pure  dry  or  moist  air  at  ordinary 
temperatures,  but  if  heated  to  redness  in  the  air,  it  rapidly 
oxidizes  to  scales  of  copper  oxide.  Steam  is  not  decomposed 
by  metallic  copper  at  a  red  heat.  Finely  divided  copper  dis 
solves  in  hydrochloric  acid  with  evolution  of  hydrogen  ;  when 


Elementary  Chemistry.  209 

heated  with  strong  sulphuric  acid,  sulphurous  dioxide  (p.  106) 
is  evolved,  and  copper  sulphate  formed  ;  and  when  acted  upon 
with  nitric  acid,  copper  nitrate  is  produced,  and  nitric  oxide 
(p.  59)  liberated. 

Many  of  the  copper  alloys  are  of  importance  ;  brass  is  an 
alloy  containing  about  two-thirds  of  copper  and  one-third  of 
zinc,  it  is  harder  than  copper  and  can  be  more  easily  worked  ; 
the  addition  of  one  to  two  per  cent,  of  lead  improves  the 
quality  of  brass  for  most  purposes.  The  yellow,  or  muntz 
metal,  used  for  the  sheathing  of  ships,  contains  sixty  per  cent, 
of  copper.  Bronze,  gun-metal,  bell-metal,  and  speculum-metal 
are  other  alloys  of  copper  and  tin  in  varying  quantities.  They 
are  all  remarkable  for  the  property  of  being  hard  and  brittle 
when  slowly  cooled,  but  of  becoming  soft  and  malleable  if  they 
are  cooled  suddenly  when  red-hot  by  dipping  into  cold  water. 

Oxides  of  Copper.  There  are  two  well-defined  oxides  ; 
cuprous  oxide,  Cu2  O,  and  cupric  oxide,  Cu  O. 

Cuprous  Oxide,  or  Red  Oxide,  Cu2  O,  occurs  native  in 
ruby-red  octohedral  crystals  ;  it  is  artificially  prepared  by 
heating  equivalent  quantities  of  cupric  oxide  and  copper  fi 
lings,  or  by  boiling  a  solution  of  copper  sulphate  and  sugar,  to 
which  excess  of  caustic  potash  has  been  added :  the  sugar 
reduces  the  copper  salt,  and  cuprous  oxide  is  precipitated  as 
a  bright  red  powder.  Cuprous  oxide  imparts  to  glass  a 
splendid  ruby-red  color  ;  it  forms  colorless  salts  with  acids 
which  rapidly  absorb  oxygen  from  the  air,  and  pass  into  the 
corresponding  cupric  compounds.  The  most  important  of 
these  salts  is  cuprous  chloride,  Cu  Cl,  a  white  solid  substance 
obtained  by  dissolving  a  mixture  of  cupric  oxide  and  metallic 
copper  in  hydrochloric  acid  :  the  solution  of  cuprous  chloride 
possesses  the  remarkable  property  of  absorbing  carbonic 
oxide  gas. 

Cupric,  or  Black  Oxide,  Cu  O.  This  oxide  is  formed  when 
copper  is  heated  in  the  air,  or  when  cupric  nitrate  is  heated 
to  redness  ;  it  yields  the  blue  and  green  cupric  salts,  and  it  is 
largely  used  in  the  laboratory  as  a  means  of  giving  oxygen  for 
the  combustion  of  organic  substances  (see  p.  236).  Hydrated 


2io  Elementary  Chemistry. 

cupric  oxide  is  obtained  as  a  light  blue  precipitate  when 
caustic  alkali  is  added  to  a  cupric  salt ;  when  this  is  heated  to 
100°  it  loses  its  water,  and  the  anhydrous  oxide  falls  as  a 
brown  powder.  Cupric  oxide  is  soluble  in  acids,  furnishing  a 
series  of  well  crystallizing  salts  ;  of  these  the  most  important 
soluble  compounds  are  :  (i)  copper  sulphate,  Cu  SO4  +  5H2  O. 
This  salt  is  sometimes  known  as  blue  vitriol,  and  is  largely 
manufactured  by  dissolving  copper  oxide  (copper  scales)  in 
sulphuric  acid.  It  crystallizes  in  large  blue  crystals  belonging 
to  the  triclinic  system  (Fig.  51)  ;  when  heated  to  redness,  it 
loses  all  its  water  of  crystallization,  and  forms  a  white  powder, 
which  again  at  a  higher  temperature  decomposes,  leaving 
copper  oxide.  Copper  sulphate  is  employed  in  calico  print 
ing,  and  in  the  manufacture  of  Scheele's  green,  and  Brunswick 
green,  and  other  copper  pigments.  The  sulphate  and  the 
other  copper  salts  give,  with  excess  of  ammonia,  a  deep-blue 
colored  solution,  forming  a  remarkable  compound,  capable  of 
crystallizing  ;  the  production  of  this  blue  color  may  be  used 
as  a  test  of  the  presence  of  copper.  (2)  Copper  nitrate,  Cu 
2  (NO3)  6  (H2O),  a  very  soluble  salt,  crystallizing  in  large  blue 
prisms  obtained  by  dissolving  copper  in  nitric  acid.  (3)  Cop 
per  chloride,  Cu  C12  +  2  H2O,  formed  when  copper  is  brought 
into  chlorine  gas,  or  when  copper  oxide  is  dissolved  in  hydro 
chloric  acid  ;  it  forms  green  needle-shaped  crystals  soluble  in 
water  and  alcohol.  The  alcoholic  solution  burns  with  a 
characteristic  green  flame.  The  insoluble  copper  salts  are  : 
(i)  the  sulphide,  Cu  S,  obtained  as  a  black  precipitate,  when 
sulphuretted  hydrogen  gas  is  passed  through  an  acidified 
solution  of  a  copper  salt ;  (2)  the  carbonate,  which,  however, 
is  not  known  in  the  pure  state,  ,as  the  green  precipitate 
obtained  by  adding  a  solution  of  an  alkaline  carbonate  to  a 
copper  salt,  always  contains  hydrated  oxide ;  the  mineral 
malachite  also  possesses  a  similar  composition  ;  (3)  copper 
arsenite,  or  Scheele's  green,  is  a  bright  green  powder  used 
as  a  pigment,  and  obtained  by  mixing  solutions  of  sodium 
arsenite  with  copper  sulphate.  The  copper  salts  act  as  pow 
erful  poisons,  and  they  may  be  detected — (i)  by  the  black 


Elementary  Chemistry.  21 1 

insoluble  sulphide  ;  (2)  by  the  blue  hydrate  turning  black  on 
heating ;  (3)  by  the  deep  blue  coloration  with  ammonia ;  (4) 
by  the  deposition  of  red  metallic  copper  upon  a  bright  surface 
of  iron  placed  in  the  solution. 

2.  MERCURY.  Symbol  Hg  (Hydrargyrum}.  Combining 
Weight  200.  Specific  Gravity  at  o°  I3'596.  Density  100.* 

The  chief  ore  of  mercury  is  the  sulphide,  or  cinnabar, 
which  occurs  at  Almaden  in  Spain,  at  Idria  in  Illyria,  in  Cali 
fornia,  and  also  in  China  and  Japan.  The  metal  is  easily 
obtained  by  roasting  the  ore,  when  the  sulphur  burns  off  as 
the  dioxide,  and  the  metal  volatilizes,  and  its  vapor  is  con 
densed  in  earthen  pipes.  Mercury  is  the  only  metal  liquid  at 
the  ordinary  temperature  ;  it  freezes  at  -40°,  crystallizing  in 
octohedra ;  in  the  solid  state  it  is  malleable  and  possesses  a 
density  of  14*4.  It  boils  at  350°  (measured  by  the  air  ther 
mometer),  and  gives  off  a  slight  amount  of  vapor  at  the 
ordinary  temperature.  The  specific  gravity  of  its  vapor  (air 
=  i)  is  6-976.  Mercury  when  pure  does  not  tarnish  in  moist 
or  dry  air,  but  when  heated  above  300°  it  slowly  absorbs 
oxygen,  passsing  into  the  red  oxide  ;  and  it  combines  directly 
with  chlorine,  bromine,  iodine,  and  sulphur.  Hydrochloric 
acid  does  not  attack  mercury ;  sulphuric  acid,  on  heating, 
forms  sulphuric  dioxide  (p.  105)  and  mercuric  sulphate  ;  and 
nitric  acid  evolves  nitric  oxide  and  forms  mercuric  nitrate. 
Mercury  is  largely  used  in  the  process  of  extracting  gold  and 
silver  from  their  ores  (p.  213),  and  in  the  arts,  for  silvering 
mirrors,  and  other  purposes.  Mercury  is  deposited  from  its 
solutions  upon  metallic  iron  or  copper,  in  the  form  of  a 
gray  powder,  which  becomes  bright  on  burnishing.  Mercury 
and  its  salts  act  as  valuable  medicines. 

Two  oxides  of  mercury  are  known  :  the  black  or  mercurous 
oxide,  Hg2  O,  and  the  red  or  mercuric  oxide,  Hg  O.  Mer 
curous  oxide  is  best  obtained  by  digesting  calomel  (mercurous 
chloride)  with  an  excess  of  caustic  alkali ;  it  forms  black 

*  The  atom  of  mercury  weighing  200  occupies  2  volumes,  and  hence  its  vapor 
density  is  half'\\s>  combining  weight. 


212  Elementary  Chemistry. 

powder,  which  undergoes  decomposition  on  exposure  to  light, 
or,  on  heating  to  100°,  into  metallic  mercury  and  the  red 
oxide.  Mercuric  oxide,  Hg  O,  is  obtained  by  moderately 
heating  the  nitrate ;  it  may  also  be  prepared  by  heating  the 
metal  to  about  300°  in  the  air,  or  by  precipitating  the  nitrate 
with  caustic  potash.  The  sulphides  correspond  to  the  oxides  ; 
mercurous  suphide,  Hg2  S,  is  an  unstable  black  compound, 
prepared  by  passing  sulphuretted  hydrogen  through  a  solu 
tion  of  mercurous  salt.  Mercuric  Sulphide,  cinnabar,  or  ver 
milion,  Hg  S,  is  a  more  important  substance.  It  occurs 
native,  and  may  be  prepared  artificially  by  heating  a  mixture 
of  sulphur  and  mercury.  When  precipitated  from  a  solution 
of  mercuric  salt  by  sulphuretted  hydrogen,  the  sulphide  is 
black,  but  on  sublimation  becomes  red.  The  chlorides  of 
mercury  are  important  compounds.  Mercurous  chloride, 
or  calomel,  Hg2Cl2,  and  mercuric  chloride,  or  corrosive 
sublimate,  HgCl2. 

Merciirous  Chloride,  Calomel,  Hg2  C12,  is  generally  pre 
pared  by  heating  a  mixture  of  three  parts  of  finely-divided 
metallic  mercury  with  four  parts  of  corrosive  sublimate  ;  the 
metal  combines  with  half  the  chlorine  of  the  corrosive  sub 
limate,  and  one  atom  of  calomel  is  formed,  Hg  C12  +  Hg  = 
Hg2  C12.  The  calomel  sublimes,  and  is  deposited  in  a  solid 
cake;  it  must  be  well  washed  in  order  to  free  it  from  any 
soluble  mercuric  chloride  which  may  remain  undecomposed. 
Calomel,  a  white  powder,  is  insoluble  in  water,  but  is  decom 
posed  by  potash  or  ammonia.  It  is  used  largely  in  medicine. 
Mercuric  Chloride,  or  Corrosive  Sublimate,  Hg  C12,  is  pre 
pared  on  a  large  scale  by  heating  an  intimate  mixture  of 
equal  parts  of  mercuric  sulphate  and  common  salt ;  it  is  also 
formed  when  mercury  burns  in  chlorine.  It  acts  as  a  violent 
poison  ;  it  is  soluble  in  water,  crystallizing  in  rectangular 
octohedra,  fuses  at  265°,  and  boils  at  295°.  The  other 
important  soluble  salts  of  mercury  are  the  mercurous  and 
mercuric  nitrates,  respectively  obtained  by  acting  on  mercury 
with  an  excess  of  dilute  nitric  acid,  and  by  dissolving  mercuric 
oxide  in  nitric  acid.  The  mercury  compounds  can  be  readily 


Elementary  Chemistiy.  213 

recognized :  (i)  by  precipitation  of  black  mercuric  sulphide, 
insoluble  in  nitric  acid  ;  (2)  by  the  reduction  of  liquid  globules 
of  the  metal  when  any  compound  is  strongly  heated  with 
sodium  carbonate  in  a  small  tube  ;  (3)  by  the  deposit  of 
metallic  mercury  on  copper.  The  mercurous  salts  are  dis 
tinguished  by  precipitating  calomel  when  a  chloride  is  added 
to  a  soluble  salt;  whilst  the  mercuric  salts  may  be  detected 
by  the  formation  of  red  mercuric  iodide. 

3.  SILVER.  Symbol  Ag.  Combining  Weight  108.  Speci 
fic  Gravity  10*5. 

Silver  was  known  to  the  ancients.  It  is  found  in  the  native 
state,  as  well  as  combined  with  sulphur,  antimony,  chlorine, 
and  bromine.  It  is  also  contained  in  small  quantities  in  ga 
lena  (p.  202),  and  it  can  be  extracted  with  profit  from  the 
lead  prepared  from  this  ore,  even  when  the  lead  contains  only 
two  or  three  ounces  of  silver  to  the  ton.  The  method  thus 
adopted  for  the  extraction  of  the  silver  depends  upon  the  fact 
that  the  whole  of  the  silver  can  be  concentrated  into  a  small 
portion  of  lead,  by  crystallization  ;  metallic  lead  free  from 
silver  separates  out  in  crystals,  and  a  rich  alloy  is  left.  When 
this  reaches  the  concentration  of  300  oz.  silver  to  the  ton,  the 
alloy  undergoes  the  operation  of  cupellation,  in  which  the 
mixture  is  melted  in  a  furnace  on  a  porous  bed  of  bone-earth, 
and  a  blast  of  air  blown  over  the  surface  :  the  lead  oxidizes, 
and  the  oxide  (litharge)  fuses,  and  partly  runs  away  and  partly 
sinks  into  the  porous  bed  of  the  furnace,  whilst  the  silver 
remains  behind  in  the  metallic  state. 

For  the  extraction  of  silver  from  the  other  ores,  a  process 
termed  amalgamation  is  employed,  in  which  mercury  is  used 
to  dissolved  the  metallic  silver.  The  argentiferous  ores  of 
Germany,  in  which  the  silver  occurs  in  combination  with  sul 
phur,  are  worked  in  a  different  manner ;  the  ore  is  roasted  in 
a  furnace  with  common  salt,  by  which  means  the  silver  sul 
phide  is  converted  into  chloride  ;  the  mixture  is  then  placed 
in  casks  made  to  revolve,  and  scrap-iron  and  water  is  added. 
The  iron  reduces  the  silver  to  the  metallic  state,  and  when 


214  Elementary  Chemistry. 

this  is  fully  accomplished,  metallic  mercury  is  added ;  this 
forms  a  liquid  amalgam  with  the  silver  (and  gold,  if  any  be 
present),  and  by  distilling  the  mercury  off,  the  silver  is  ob 
tained  in  an  impure  state.  A  somewhat  different  method  is 
employed  in  South  America,  where  fuel  is  expensive.  Silver 
possesses  a  bright  white  color  and  a  brilliant  lustre,  which  it 
does  not  lose  in  pure  air  at  any  temperature,  but  when  melted 
in  the  air  it  possesses  the  singular  power  of  absorbing  mecha 
nically  a  large  volume  (twenty-two  times  its  bulk)  of  oxygen  ; 
this  gas  it  again  gives  out  on  solidifying,  a  phenomenon  tech 
nically  known  as  the  "spitting"  of  silver. 

Silver  is  probably  the  best  conductor  of  heat  and  electricity 
known,  and  is  extremely  ductile  ;  one  gramme  of  metal  can 
be  drawn  out  into  a  wire  of  2,600  metres  in  length.  Sulphur 
combines  at  once  with  silver,  forming  a  black  sulphide  ;  silver 
articles  long  exposed  to  the  air  tarnish  from  this  cause. 
Silver  is  easily  soluble  in  nitric  acid,  the  nitrate  being  formed 
and  nitric  oxide  gas  being  evolved. 

Alloys  of  Silver.  Silver  itself  is  largely  used  in  the  pure 
state  for  various  purposes  in  the  arts,  but  it  is  usually  alloyed 
with  a  small  quantity  of  copper  when  employed  as  coin  or  for 
articles  of  plate.  The  English  coinage  contains  7-5  per  cent 
of  copper  in  the  standard  silver,  whilst  the  French  contains  10 
per  cent. 

Silver  forms  two  compounds  with  oxygen,  Ag4O  and  Ag2O. 
The  first  of  these  is  called  silver  snboxide,  it  is  a  black  pow 
der  which  readily  undergoes  decomposition  ;  the  second, 
termed  silver  oxide,  is  obtained  in  the  form  of  a  brown  pre 
cipitate,  when  caustic  potash  is  added  to  a  solution  of  silver 
nitrate.  From  this  oxide,  which  is  decomposed  into  metal 
and  oxygen  on  heating,  the  ordinary  silver  salts  may  be 
derived  by  dissolving  in  acids.  Silver  nitrate,  Ag  NO3,  is 
the  most  important  soluble  salt  of  silver.  It  is  obtained  in 
the  form  of  large  transparent  tabular  crystals  on  evaporating 
a  solution  of  silver  in  nitric  acid,  and  is  soluble  in  its  own 
weight  of  cold  and  half  its  weight  of  hot  water,  and  in  four 
parts  of  alcohol.  Silver  nitrate  fuses  easily  on  heating,  and 


Elementary  Chemistry.  215 

when  cast  into  sticks  goes  by  the  name  of  lunar  caustic.  This 
salt  undergoes  decomposition  when  exposed  to  the  sunlight 
in,  contact  with  organic  matter,  and  a  black  substance,  prob 
ably  consisting  of  the  suboxide,  is  formed  ;  hence  it  is  em 
ployed  in  the  manufacture  of  an  indelible  ink  for  marking 
linen  and  other  fabrics. 

Of  the  insoluble  silver  salts,  the  chloride,  Ag  Cl,  is  the 
most  important.  This  salt  occurs  in  nature,  and  is  then 
known  as  horn  silver,  and  is  precipitated  as  a  white  curdy 
mass  when  a  solution  of  a  chloride  and  a  silver  salt  are 
brought  together.  When  exposed  to  sun-  or  daylight,  the 
white  chloride  becomes  tinted  of  a  purple  color,  which  in 
creases  in  shade  as  the  action  of  light  continues  ;  this  colora 
tion  arises  from  a  partial  decomposition  of  the  salt,  a  small 
quantity  of  subchloride  and  free  hydrochloric  acid  being 
formed  ;  in  presence  of  organic  matter  this  change  takes 
place  much  more  rapidly,  and  upon  this  fact  the  phenomena 
of  photography  depend.  Silver  chloride  fuses  at  about  260°, 
and  at  higher  temperatures  volatilizes  ;  it  is  easily  reduced  to 
metallic  silver  in  presence  of  zinc  and  sulphuric  acid.  The 
chloride  is  perfectly  insoluble  in  pure  water,  but  it  dissolves 
appreciably  in  strong  hydrochloric  acid  and  in  a  solution  of 
common  salt,  whilst  it  dissolves  easily  in  ammonia  ;  it  is  also 
easily  soluble  in  a  solution  of  sodium  hyposulphite,  and  it  is 
for  this  reason  that  the  latter  salt  is  used  for  "fixing"  photo 
graphic  pictures,  that  is,  dissolving  out  the  unaltered  silver  salt, 
and  thus  rendering  the  image  permanent.  Silver  bromide, 
Ag  Br,  falls  as  a  white  precipitate  when  silver  nitrate  is  added 
to  an  alkaline  bromide  ;  it  is  also  acted  upon  by  the  light, 
and  is  soluble  in  ammonia  and  an  alkaline  hyposulphite.  The 
iodide,  Agl,  is  a  yellow  powder,  insoluble  in  water  and  am 
monia,  but  dissolved  by  an  alkaline  hyposulphite.  Silver 
sulphide,  Ag2S,  occurs  native  in  cubic  crystals,  as  silver 
glance  ;  it  is  precipitated  as  a  black  powder  by  passing  sul 
phuretted  hydrogen  through  solutions  of  the  salts  of  silver. 
Silver  can  be  easily  detected  when  in  solution  by  the  precipi 
tation  of  the  white  curdy  chloride,  insoluble  in  water  and 


2i6  Elementary  Chemistry. 

nitric  acid,  and  soluble  in  ammonia :  the  metal  can  be  easily 
obtained  in  malleable  globules  before  the  blowpipe,  whilst  it 
is  reduced  from  its  solutions  by  iron,  copper,  and  mercury. 
Silver  is  always  estimated  quantitatively  either  as  the  chloride 
or  as  the  metal. 


XI.  GROUP,     i,  GOLD.    2,  PLATINUM,  AND  THE  RARE 
PLATINUM-LIKE  METALS. 

I.  GOLD.  Symbol  Au  (Aurwri).  Combining  Weight  197. 
Specific  Gravity  19*3. 

Gold  is  always  found  in  the  metallic  state  ;  it  occurs  in 
veins  in  the  older  sedimentary  or  in  the  plutonic  rocks,  and 
in  the  detritus  of  such  rocks  ;  it  occurs  in  traces  in  the  sand 
of  most  rivers,  and  although  found  generally  in  small  quanti 
ties,  it  is  a  widely  diffused  metal.  Previous  to  the  dis 
coveries  of  the  gold-fields  of  California  and  Australia,  it  was 
obtained  from  certain  iron  pyrites.  In  order  to  obtain  the 
gold,  the  detritus  or  sand  which  contains  the  metal  is  washed 
in  a  u  cradle  "  or  other  arrangement,  by  means  of  which  the 
lighter  particles  of  mud  or  mineral  are  washed  away,  whilst 
the  heavier  grains  of  gold  sink  to  the  bottom  of  the  vessel. 
When  gold  has  to  be  worked  in  the  solid  rock,  the  mineral  is 
crushed  to  powder  and  then  shaken  up  with  mercury,  and  the 
gold  thus  extracted  by  amalgamation. 

Gold  possesses  a  brilliant  yellow  color,  and,  in  thin  films, 
transmits  green  light ;  it  is  nearly  as  soft  as  lead  ;  it  can  be 
drawn  out  into  fine  wire,  and  is  the  most  malleable  of  all  the 
metals.  It  does  not  tarnish  at  any  temperature,  in  dry  or 
moist  air,  nor  is  it  affected  by  sulphur  like  silver ;  it  is  not 
acted  upon  by  any  single  acid  (except  selenic),  but  dissolves 
in  presence  of  free  chlorine  and  in  nitro-hydrochloric  acid. 
At  high  temperatures  gold  is  slightly  volatile.  Pure  gold  is  best 
prepared  by  dissolving  the  ordinary  metal  in  aqua  regia,  and 
adding  ferrous  sulphate,  which  is  oxidized  to  ferric  salt  and 
precipitates  the  gold  as  a  brown  powder.  The  standard  gold 


'Elementary  Chemistry.  217 

of  our  country  is  an  alloy  of  gold  and  copper  in  the  propor 
tion  of  1 1  of  gold  to  i  of  copper,  or  8-33  per  cent,  of  the  latter 
metal ;  this  alloy  is  harder  and  more  fusible,  but  less  ductile 
than  pure  gold. 

Gold  unites  with  oxygen  in  two  proportions,  forming  Gold 
suboxide,  Au2  O,  and  Gold  oxide,  Aua  O3.  Neither  of  these 
oxides  forms  salts  with  acids  ;  but  the  latter  unites  with  bases 
to  form  compounds  called  Aurates.  Gold  oxide  is  obtained 
by  adding  zinc-oxide  or  magnesia  to  a  solution  of  gold  chlo 
ride  :  the  oxide  falls  as  a  brown  powder,  from  which  the  zinc 
can  be  separated  by  nitric  acid.  Gold  oxide  decomposes,  in 
direct  sunlight,  into  metal  and  oxygen,  and  is  also  reduced 
when  heated  to  a  temperature  of  about  250°.  The  most  im 
portant  compound  of  gold  oxide  is  fulminating  gold  ;  this 
substance  is  obtained  by  acting  on  a  solution  of  gold  with 
excess  of  ammonia ;  a  yellow-brown  powder  is  precipitated, 
which,  when  dry,  explodes  very  easily  when  heated  to  100°, 
or  when  struck  with  a  hammer.  There  are  two  gold  chlorides 
known  :  (i)  gold  chloride,  Au  Cl,  obtained  as  an  insoluble 
white  mass  when  gold  trichloride  is  heated  to  the  melting 
point  of  tin  ;  (2)  the  trichloride,  AuCl3,  obtained  when  gold 
is  dissolved  in  aqua  regia.  This  is  the  most  important  com 
pound  of  gold.  On  evaporating  the  solution,  crystals  of  a 
compound  of  gold  trichloride  and  hydrochloric  acid,  are  de 
posited.  Gold  trichloride  also  forms  crystalline  compounds 
with  the  alkaline  chlorides.  Gold  salts  can  be  easily  recog 
nized  by  the  brown  precipitate  of  metallic  gold  formed  on 
addition  of  ferrous  salts,  which  can  be  reduced  to  a  globule 
before  the  blowpipe  ;  and  also  by  the  formation  of  a  purple 
color  (purple  of  Cassius),  when  gold  trichloride  is  added  to  a 
dilute  solution  of  a  mixture  of  the  two  tin  chlorides. 

2.  PLATINUM.  Symbol  Pi.  Combining  Weight  197^4.  Spe 
cific  Gravity  2i'$. 

Platinum  is  a  comparatively  rare  metal,  which  always  oc 
curs  in  the  native  state,  and  generally  alloyed  with  five  other 
metals,  viz.,  palladium,  rhodium,  iridium,  osmium,  and  ruthe- 

10 


218  Elementary  Chemistry. 

nium.  This  alloy  occurs  in  small  grains  in  detritus  and  gravel 
in  Siberia  and  Brazil ;  it  has  not  been  found  in  situ  in  the 
original  rock,  which  probably  belongs  to  the  old  plutonic 
series. 

The  original  mode  of  obtaining  the  metal  was  to  dissolve 
the  ore  in  aqua  regia,  and  precipitate  the  platinum  (together 
with  several  of  the  accompanying  metals)  with  sal-ammoniac, 
as  the  insoluble  double  chloride  of  ammonium  and  platinum, 
2NH4C1,  PtCh.  This  precipitate,  on  heating,  yields  metallic 
platinum  in  a  finely  divided  or  spongy  state,  and  this  sponge, 
if  forcibly  pressed  and  hammered  when  hot,  gradually  as 
sumes  a  coherent  metallic  mass,  the  particles  of  platinum 
welding  together,  when  hot,  like  iron.  A  new  mode  of  pre 
paring  the  metal  has  recently  been  proposed,  the  ore  being 
melted  in  a  very  powerful  furnace  heated  with  the  oxyhydrogen 
blowpipe.  In  this  way  a  pure  alloy  of  platinum,  iridium,  and 
rhodium  is  formed,  the  other  constituents  and  impurities  of 
the  ore  either  being  volatilized  by  the  intense  heat,  or  absorbed 
by  the  lime  of  which  the  crucible  is  composed.  This  alloy  is 
in  many  respects  more  useful  than  pure  platinum,  being  harder 
and  less  easily  attacked  by  acids  than  the  pure  metal. 

Platinum  possesses  a  bright  white  color,  and  does  not 
tarnish  under  any  circumstances  in  the  air  ;  it  is  extremely 
infusible,  and  can  only  be  melted  by  the  heat  of  the  oxy 
hydrogen  blowpipe.  It  is  unacted  upon  by  the  ordinary  acids, 
but  dissolves  in  aqua  regia,  and  hence  platinum  vessels  are 
much  used  in  the  laboratory.  Caustic  alkalies,  however,  act 
upon  the  metal  at  high  temperatures.  When  finely  divided, 
•metallic  platinum  has  the  power  of  condensing  gases  on  to 
its  surface  in  a  remarkable  degree  ;  the  effect  of  bringing 
spongy  platinum  in  contact  with  a  mixture  of  oxygen  and 
hydrogen  has  already  been  mentioned.  Platinum  and  oxygen 
unite  in  two  proportions  to  form — (i)  Platinous  Oxide,  Pt  O  ; 
and  (2)  Platinic  Oxide,  Pt  O2.  The  first  of  these  oxides  is  a 
black  powder,  easily  decomposed  on  heating,  and  yielding  a 
series  of  unstable  salts  ;  the  second  is  obtained  as  a  brown 
hydrate,  by  adding  to  a  solution  of  platinic  nitrate  half  its 


Elementary  Chemistry.  219 

equivalent  of  caustic  potash  ;  the  hydrate,  when  heated,  first 
loses  its  water,  forming  the  anhydrous  oxide,  and  then  parts 
with  its  oxygen,  leaving  the  metal.  Platinous  chloride,  PtCl2, 
is  a  green  insoluble  powder,  obtained  by  heating  the  higher 
chloride  to  200°  ;  platinic  chloride,  PtCl4,  is  the  most  impor 
tant  platinum  compound.  It  is  obtained  as  a  yellowish-red 
solution  by  dissolving  the  metal  in  aqua  regia  ;  on  evapora 
tion,  crystals  of  a  compound  of  platinic  chloride  with  hydro 
chloric  acid  separate  out.  The  platinic  chloride  combines  with 
many  alkaline  chlorides  to  form  double  salts  ;  these  compounds 
with  potassium,  rubidium,  caesium,  and  ammonium,  are  insoluble 
in  water,  and  are  isomorphous,  crystallizing  in  cubes,  whilst 
the  sodium  salt  is  soluble  and  crystallizes  in  large  prisms. 

Platinous  chloride,  when  acted  upon  by  ammonia,  gives  rise 
to  several  very  remarkable  compounds,  containing  platinum, 
nitrogen,  and  hydrogen  ;  these  substances  act  as  bases,  and 
form  a  well-defined  series  of  salts.  These  bases  may  be 
considered  as  molecules  of  ammonia,  in  which  the  hydrogen 
has  been  partly  replaced  by  either  a  diatomic  or  tetratomic 
platinum. 

For  the  properties  of  the  rare  metals  palladium,  rhodium, 
ruthenium,  iridium,  and  osmium,  the  larger  manuals  must 
be  consulted. 


LESSON   XXVI. 
SPECTRUM  ANALYSIS. 

AN  entirely  new  branch  of  chemical  analysis,  of  great 
delicacy  and  importance,  has  recently  been  developed,  chiefly 
by  the  researches  of  Bunsen  and  Kirchhoff,  the  principles  of 
which  may  here  be  shortly  stated. 

It  has  long  been  known  that  certain  chemical  substances, 
especially  the  salts  of  the  alkalies  and  alkaline  earths,  when 
strongly  heated  in  the  blowpipe,  or  other  nearly  colorless 


22O  Elementary  Chemistry. 

flame,  impart  to  that  flame  a  peculiar  color,  by  the  occurrence 
of  which  the  presence  of  the  substance  may  be  detected  ;  if 
many  of  these  substances  are  present  together  the  detection 
of  each  by  the  naked  eye  becomes  impossible,  owing  to  the 
colors  being  blended  and  thus  interfering  with  each  other. 
Thus,  for  instance,  the  sodium  compounds  color  the  flame 
an  intense  yellow,  whilst  the  potassium  salts  tinge  the  flame 
violet ;  the  yellow  soda  color  is,  however,  so  much  more 
intense  than  the  purple  potash  tint,  that  a  small  trace  of  soda 
prevents  the  eye  from  detecting  the  purple,  even  if  large 
quantities  of  potash  salts  are  present.  This  difficulty  is  alto 
gether  overcome,  and  this  method  of  observation  rendered 
extremely  sensitive,  if,  instead  of  regarding  the  flame  with  the 
naked  eye,  it  is  examined  through  a  prism.  This  consists  of 
a  triangular  piece  of  glass,  in  passing  through  which  the  light 
is  refracted,  or  bent  out  of  its  course— each  differently  colored 
ray  being  differently  refracted,  so  that  if  a  source  of  white 
light,  such  as  the  flame  of  a  candle  is  thus  regarded,  a  con 
tinuous  band  of  differently  colored  rays  is  observed — the 
compound  white  light  being  resolved  into  all  its  variously 
colored  constituents.  This  colored  band  is  termed  a  Spec- 
trum,  and  each  source  of  pure  white  light  gives  the  same 
continuous  spectrum,  stretching  from  red  (the  least  refrangible) 
to  violet  (the  most  refrangible)  color,  identical  in  fact  with 
the  colors  of  the  rainbow. 

If  these  colored  flames  are  examined  by  means  of  a  prism, 
the  light  being  allowed  to  fall  through  a  narrow  slit  upon  the 
prism,  it  is  at  once  seen  that  the  light  thus  refracted  differs 
essentially  from  white  light,  inasmuch  as  it  consists  of  only  a 
particular  set  of  rays,  each  flame  giving  a  spectrum  contain 
ing  a  few  bright  bands.  Thus  the  spectrum  of  the  yellow 
soda  flame  contains  only  one  fine  bright  yellow  line,  whilst  the 
purple  potash  flame  exhibits  a  spectrum  in  which  there  are  two 
bright  lines,  one  lying  at  the  extreme  red,  and  the  other  at  the 
extreme  violet  end.  These  peculiar  lines  are  always  pro 
duced  by  the  san:-e  chemical  element,  and  by  no  other  known 
substance  ;  and  the  position  of  these  lines  always  remains 


Elementary  Chemistry.  221 

unaltered.  When  the  spectrum  of  a  flame  tinted  by  a  mixture 
of  sodium  and  potassium  salts  is  examined,  the  yellow  ray  of 
sodium  is  found  to  be  confined  to  its  own  position,  whilst  the 
potassium  red  and  purple  lines  are  as  plainly  seen  as  they 
would  have  been  had  no  sodium  been  present 

The  colored  flames  which  are  exhibited  by  the  salts  of 
lithium,  barium,  strontium,  and  calcium,  likewise  each  give 
rise  to  a  peculiar  spectrum,  by  means  of  which  the  presence 
or  absence  of  very  small  quantities  of  these  substances  can  be 
ascertained  with  certainty  when  mixed  together,  simply  by 
observing  the  presence  or  absence  of  the  peculiar  bright 
bands  characteristic  of  the  particular  body. 

The  advantage  which  this  new  method  of  analysis  possesses 
over  the  older  processes  lies  in  the  extreme  delicacy,  as  well 
as  in  the  great  facility,  with  which  the  presence  of  particular 
elements  can  be  detected  with  certainty.  Thus  a  portion  of 

sodium  salt  less  than  the  - — th  part  of  a  grain  can  be 

100,000,000 

detected  ;  and  compounds  are  found  to  be  most  widely  dis 
seminated  throughout  the  earth,  which  were  supposed  to 
occur  very  seldom.  The  extreme  delicacy  of  the  method  is 
seen  when  we  learn  that  every  substance  which  has  even  been 
exposed  to  the  air  for  a  moment  gives  the  soda  line,  when 
placed  in  a  colorless  flame  ;  and  when  we  find  that  the 
lithium  compounds,  which  were  formerly  supposed  to  be  con 
tained  in  only  four  minerals,  by  aid  of  spectrum  analysis  are 
found  to  be  substances  of  most  common  occurrence,  being  ob 
served  in  almost  all  spring  waters,  in  tea,  tobacco,  milk,  and 
blood,  but  existing  in  such  minute  quantities  as  to  have  alto 
gether  eluded  recognition  by  the  older  and  less  delicate 

analytical  methods.  "6  ^  ^th  part  of  a  grain  of  lithium  can 
thus  be  detected.  A  still  more  striking  proof  of  the  value  of 
spectrum  analysis  lies  in  the  fact  of  the  recent  discovery  of 
four  new  elementary  bodies  by  its  means  ;  two  new  alkaline 
metals,  rubidium  and  caesium,  having  been  found,  together 
with  potash  and  soda  in  certain  mineral  springs,  and  two  new 
metals,  thallium  and  indium,  having  been  respectively  de- 


222  Elementary  Chemistry. 

tected  in  iron  pyrites  and  zinc  ores.  The  new  alkaline 
metals  resemble  potassium  so  closely  in  their  properties, 
that  it  would  be  nearly  impossible  to  have  detected  them  by 
the  ordinary  analytical  methods,  although  their  spectra  exhibit 
very  distinct  bright  bands  not  seen  in  the  potassium  or  any 
other  known  spectrum.  The  metal  thallium  was  discovered 
by  observing  a  splendid  green  line  which  did  not  belong  to 
any  known  substance  ;  whilst  indium  was  recognized  by  the 
presence  of  a  hitherto-unobserved  fine  dark  blue  line. 

It  is  not  only  those  bodies  which  have  the  power  of  im 
parting  color  to  a  flame  which  yield  characteristic  spectra,  for 
this  property  belongs  to  every  elementary  substance,  whether 
metal  or  non-metal,  solid,  liquid,  or  gas  ;  and  it  is  always 
observed  when  such  element  is  heated  to  the  point  at  which 
its  vapor  becomes  luminous,  for  then  each  element  emits  the 
peculiar  light  given  off  by  it  alone,  and  the  characteristic 
bright  lines  become  apparent  when  its  spectrum  is  observed. 
Most  metals  require  a  much  higher  temperature  than  the 
common  flame,  in  order  that  their  vapors  should  become  lumi 
nous  ;  but  they  may  be  easily  heated  up  to  the  requisite 
temperature  by  means  of  the  electric  spark,  which,  in  passing 
between  two  points  of  the  metal  in  question,  volatilizes  a 
small  portion,  and  heats  it  so  intensely  as  to  enable  it  to  give 
off  its  peculiar  light.  Thus  all  the  metals,  among  others  iron, 
platinum,  silver,  and  gold,  may  each  be  recognized  by  the 
peculiar  bright  lines  which  their  spectra  exhibit. 

The  permanent  gases  also  yield  characteristic  spectra  when 
they  are  strongly  heated,  as  by  the  passage  of  an  electric 
spark  ;  thus,  if  the  spark  be  passed  through  an  atmosphere 
of  hydrogen  gas,  the  light  emitted  is  bright  red,  and  its  spec 
trum  consists  of  one  bright  red,  one  green,  and  one  blue  line  ; 
whilst  in  nitrogen  gas  the  spark  has  a  purple  color,  and  the 
peculiar  and  complicated  spectrum  of  nitrogen  is  observed 
when  this  spark  is  examined  with  a  prism. 

The  instrument  used  in  these  experiments  is  termed  a 
spectroscope.  It  consists  of  a  prism  (A,  Fig.  57),  fixed  upon  a 
firm  iron  stand,  and  a  tube  (B)  carrying  the  slit  (D)  through 


Elementary  Chemistry.  223 

which  the  rays  from  the  colored  flame  (E)  fall  upon  the  prism, 
and  being  rendered  parallel  by  passing  through  a  lens.  The 
light,  having  been  refracted,  is  received  by  the  telescope  (F), 
and  the  image  magnified  before  reaching  the  eye.  For  exact 


FIG.  57- 

experiments,  the  number  of  prisms  and  the  magnifying  power 
are  increased,  and  arrangements  made  for  bringing  two 
spectra  into  the  field  of  view  at  once,  so  as  to  be  able  to 
make  any  wished-for  comparison  of  the  lines. 

As  none  of  these  lines  overlie  one  another,  if  any  number 
of  different  substances  were  present  together  in  a  flame,  it 
would  be  easy  to  detect  the  presence  of  each  ingredient  by 
the  appearance  of  all  its  characteristic  lines. 

Solar  and  Stellar  Chemistry. 

If  sunlight  be  allowed  to  fall  upon  the  slit  of  the  spectro 
scope,  it  is  observed  that  the  solar  spectrum  thus  obtained 
differs  essentially  from  the  spectra  which  we  have  hitherto 
considered,  inasmuch  as  it  consists  of  a  band  of  bright  light, 
passing  from  red  to  violet,  but  intersected  by  a  very  large 
number  of  fine  black  lines,  of  different  degrees  of  breadth 
and  shade,  which  are  always  present,  and  always  occupy 
exactly  the  same  relative  position  in  the  solar  spectrum.  These 


224  Elementary  Chemistry. 

lines  indicate  the  absence  in  sunlight  of  particular  rays,  and 
they  may  be  considered  as  shadows,  or  spaces  where  there  is 
no  light ;  they  are  called  "  Fraunhofer1  s  "  lines,  after  a  German 
optician,  who  first  satisfactorily  mapped  and  described  them. 

In  the  last  few  years  the  existence  of  these  lines  has  be 
come  a  matter  of  great  importance  and  interest,  as  it  is  by 
their  help  that  the  determination  of  the  chemical  constitution 
of  the  sun  and  far-distant  fixed  stars  has  become  possible. 
The  spectra  of  the  moon  and  planets  (reflected  sunlight)  are 
found  to  exhibit  these  same  lines  in  unaltered  position,  whilst 
in  the  spectra  of  the  fixed  stars,  dark  lines  also  occur,  but 
these  stellar  lines  are  different  from  those  seen  in  direct  and 
reflected  sunlight.  Hence  the  conclusion  has  been  long 
drawn  that  the  Fraunhofer's  lines  are  in  some  way  produced 
in  the  body  of  the  sun  itself;  but  it  is  only  recently  that 
the  cause  of  their  production  has  been  discovered  by  Kirch- 
hoff,  and  thus  the  foundation  laid  for  the  science  of  solar  and 
stellar  chemistry. 

If  the  positions  of  these  dark  lines  in  the  solar  spectrum 
be  carefully  compared  in  a  powerful  spectroscope  with  those 
of  the  bright  lines  in  the  spectra  of  certain  metals,  such  as 
sodium,  iron,  and  magnesium,  it  is  seen  that  each  of  the 
bright  lines  of  the  particular  metal  coincides  not  only  in  posi 
tion,  but  also  in  breadth  and  intensity,  with  a  dark  solar  line  ; 
so  that  if  the  apparatus  be  so  arranged  that  a  solar  and 
metallic  spectrum  be  both  allowed  to  fall,  one  below  the 
other  in  the  field  of  the  telescope,  the  bright  lines  of  the 
metal  are  all  seen  to  be  continued  in  dark  solar  lines.  In  the 
case  of  metallic  iron  alone,  more  than  sixty  such  coincidences 
have  been  observed,  and  the  higher  the  magnifying  power 
employed,  the  more  striking  and  exact  does  this  coincidence 
appear. 

With  other  metals — such,  for  instance,  as  gold,  antimony, 
lithium — no  single  coincidence  can  be  noticed,  whilst  all  the 
lines  of  certain  other  metals  have  their  dark  representatives 
in  the  sun.  From  these  facts,  it  is  clear  that  there  must  be 
some  kind  of  connection  between  the  bright  lines  of  these 


Elementary  Chemistry.  22$ 

metals  and  the  coincident  dark  solar  lines,  as  such  coin 
cidences  cannot  be  the  result  of  mere  chance.  Is  the  coin 
cidence  of  the  dark  solar  lines  with  the  bright  iron  lines 
caused  by  the  presence  of  iron  in  the  sun  ?  And  if  so,  how 
do  the  lines  come  to  appear  dark  in  the  solar  spectrum  ? 

The  explanation  of  this  is  given  by  an  experiment,  in 
which  the  bright  metallic  lines  are  reversed,  or  changed  into 
dark  lines.  Thus  the  bright  yellow  soda  lines  (coincident 
with  Fraunhofer's  line  D)  can  be  made  to  appear  as  a  dark 
line,  by  allowing  the  rays  from  a  strong  source  of  white  light 
(such  as  the  oxyhydrogen  light)  to  pass  through  a  flame 
colored  by  soda,  and  then  to  fall  upon  the  slit  of  the  spec 
troscope.  Instead  of  then  seeing  the  usual  soda  spectrum  of 
a  bright  yellow  double-line  upon  a  dark  ground,  a  double 
dark  line,  identical  in  position  and  breadth  with  the  soda  line, 
will  be  seen  to  intersect  the  continuous  spectrum  of  the  white 
light.  Here  then  the  yellow  flame  has  absorbed  the  same 
kind  of  light  as  it  emits,  a  consequent  diminution  of  intensity 
in  that  part  of  the  spectrum  occurred,  and  a  dark  line  made 
its  appearance.  In  like  manner  the  spectra  of  many  other 
substances  have  been  reversed,  each  substance  in  the  state  of 
vapor  having  the  power  of  absorbing  the  same  rays  it  emits, 
or  being  opaque  for  such  rays. 

The  explanation  of  the  existence  of  dark  lines  in  the  solar 
spectrum,  coincident  with  bright  metallic  lines,  now  becomes 
evident :  these  dark  lines  are  caused  by  the  passage  of  white 
light  through  the  glowing  vapor  of  the  metals  in  question, 
present  in  the  sun's  atmosphere,  and  these  vapors  absorb 
exactly  the  same  kind  of  ligjit  which  they  are  able  to  emit. 
The  sun's  atmosphere,  therefore,  contains  these  metals  in  the 
condition  of  glowing  gases,  the  white  light  proceeding  from 
the  solid  or  liquid  strongly-heated  mass  of  the  sun  which 
lies  in  the  interior. 

By  observing  the  coincidences  of  these  dark  lines  with  the 
bright  lines  of  terrestrial  metals,  we  arrive  at  a  knowledge  of 
the  occurrence  of  such  metals  in  the  solar  atmosphere  with  as 
great  a  degree  of  certainty  as  we  are  able  to  attain  to  in  any 

10* 


226  Elementary  Chemistry. 

question  of  physical  science.  The  metals  hitherto  detected 
in  the  sun's  atmosphere  are  nine  in  number,  viz.,  iron,  sodium, 
magnesium,  calcium,  chromium,  nickel,  barium,  copper,  and 
zinc.  Hydrogen  is  also  known  to  exist  in  the  sun. 

Stellar  Chemistry.  The  same  methods  of  observation  and 
reasoning  apply  to  the  determination  of  the  chemical  consti 
tution  of  the  atmospheres  of  the  fixed  stars,  as  these  are  self- 
luminous  suns  ;  but  the  experimental  difficulties  are  greater, 
and  the  results,  therefore,  are  as  yet  less  complete,  though 
not  less  conclusive,  than  is  the  case  with  our  sun. 

The  spectra  of  the  stars  all  contain  dark  lines,  but  these 
are  for  the  most  part  different  from  the  solar  lines,  and  differ 
from  one  another ;  hence  we  conclude  that  the  chemical  con 
stitution  of  the  solar  and  stellar  atmospheres  is  different. 
Many  of  the  substances  known  on  this  earth  have  been  de 
tected  in  the  atmosphere  of  the  stars,  by  Mr.  Huggins  and 
Professor  W.  A.  Miller,  to  whom  we  owe  this  most  impor 
tant  discovery.  Thus  the  star  called  Aldebaran  contains 
hydrogen,  sodium,  magnesium,  calcium,  iron,  tellurium,  anti 
mony,  bismuth,  and  mercury;  whilst  in  Sirius  only  sodium,  mag 
nesium,  and  hydrogen  have  with  certainty  been  detected. 

In  examining  the  spectra  of  some  of  the  nebulae,  a  striking 
difference  is  observed  :  the  stellar  spectra,  it  will  be  re 
membered,  resemble  the  spectrum  of  the  sun,  inasmuch  as 
each  consists  of  a  bright  ground  intersected  with  dark  lines  ; 
the  spectra  of  the  nebulas,  on  the  other  hand,  consist  simply 
of  bright  lines,  like  the  spectra  of  hydrogen,  nitrogen,  or 
any  of  the  metals.  Hence  we  conclude  that  the  nebulae  are 
masses  of  glowing  gas,  and  do  not  consist,  like  the  sun  and 
stars,  of  a  solid  or  liquid  mass, 'surrounded  by  a  gaseous  at 
mosphere. 

The  whole  subject  of  solar  and  stellar  chemistry  is  still  in 
its  earliest  infancy,  but  the  results  already  obtained  lead  to 
the  belief  that  our  knowledge  of  the  chemical  composition 
of  those  far-distant  bodies  will  become  more  intimate  as 
the  methods  of  experiment  and  observation  are  gradually 
perfected. 


Elementary  Chemistry.  227 


LESSON  XXVII. 

CHEMISTRY  OF  THE  CARBON  COMPOUNDS,  OR 
ORGANIC    CHEMISTRY. 

ORGANIC  CHEMISTRY  is  defined  as  the  chemistry  of  the 
cafbon  compounds.  Many  of  these  compounds  exist  already 
formed  in  the  bodies  of  plants  and  animals,  and  hence  the 
name  of  Organic  Chemistry  was  given  to  this  branch  of  the 
science.  It  is  separated  from  the  foregoing,  Inorganic  por 
tion,  not  because  any'real  difference  exists  in  the  laws  re 
gulating  the  formation  of  the  bodies  classed  under  these  two 
great  divisions,  but  because  the  number  of  compounds  which 
have  to  be  studied  under  organic  chemistry  is  so  large,  and 
their  constitution  frequently  so  complicated,  that  they  are  at 
present  best  considered  after  the  more  simple  inorganic  com 
pounds  have  been  described. 

Certain  organic  substances  do,  indeed,  differ  fundamentally 
in  constitution  and  mode  of  formation  from  any  inorganic 
compound,  inasmuch  as  these  exhibit  what  is  termed  an  or- 
ganized  structure,  being  the  sole  and  direct  product  of  animal 
or  vegetable  life.  Such  an  organized  structure  is  seen  in  the 
simple  cell,  the  germ  of  living  organisms.  It  cannot  be  arti 
ficially  prepared  from  its  elementary  constituents,  whereas 
any  crystalline  or  liquid  organic  body  may  possibly  be  thus 
built  up  from  its  elements. 

The  first  striking  peculiarity  which  the  carbon  compounds 
exhibit,  is  their  extraordinary  number,  those  already  known 
far  exceeding  all  the  compounds  of  the  other  elements  taken 
together,  and  new  ones  being  daily  brought  to  light.  A 
second  peculiarity  of  these  compounds  is;  that  they  are  al 
most  all  of  them  formed  by  the  union  of  carbon  in  different 
proportions  with  one  or  more  of  three  other  elements ;  viz., 
hydrogen,  oxygen,  and  nitrogen. 

The  cause  of  the  multiplicity  of  the  carbon  compounds  is 
to  be  sought  in  a  fundamental  and  distinctive  property  of 
carbon  itself.  This  consists  in  the  power  which  this  element 


228  Elementary  Chemistry. 

possesses,  in  a  much  higher  degree  than  any  of  the  others,  of 
uniting  with  itself  to  form  complicated  compounds,  contain 
ing  an  aggregation  of  carbon  atoms  united  with  either  hydro 
gen,  oxygen,  nitrogen,  or  several  of  these,  bound  together  to 
form  a  distinct  chemical  whole.  These  molecules,  or  groups 
of  atoms,  play  in  organic  chemistry  a  part  similar  to  that  of 
the  metals  or  the  simple  molecules,  such  as  the  radicals  NOs 
and  SO;.,  met  with  in  the  inorganic  department  of  the  science  ; 
they  form  whole  series  of  compounds,  in  each  of  which  the 
group  of  atoms  can  always  be  identified,  and  in  all  the  family 
likeness  recognized.  Hence  organic  chemistry  was  formerly 
called  the  chemistry  of  the  compound  radicals,  a  name  given 
to  these  groups  of  atoms,  which  act  as  if  they  were  elements. 

We  have  already  seen  (p.  138),  that  the  atoms  of  different 
elements  possess  different  powers  of  combination  or  atomi 
cities  j  that  is,  one  atom  of  an  element  is  capable  of  replacing 
either  one  or  more  atoms  of  hydrogen  in  combinations  :  thus 
Chlorine,  Potassium,  and  Silver  are  monads,  or  can  replace 
only  one  atom  of  hydrogen  ;  whilst  Oxygen,  Sulphur,  and 
Magnesium  are  dyad  elements,  capable  of  replacing  two  of 
hydrogen  ;  and  Nitrogen,  Phosphorus,  and  Aluminium  are 
triads,  or  play  the  part  of  three  atoms  of  hydrogen.  Carbon, 
on  the  other  hand,  is  a  tetrad,  or  tetratomic  element  ;  and  just 
as  the  compounds  HC1,  H2O,  H3N  are  the  representatives  of 
the  compounds  of  the  monad,  dyad,  and  triad  elements,  so 
marsh  gas,  H4C,  is  the  characteristic  and  representative  com 
pound  of  tetratomic  carbon. 

In  this  compound  the  four  combining  units  of  the  carbon 
atom  are  saturated,  or  satisfied,  by  union  with  the  four  atoms 
of  hydrogen,  and  hence  this  is  said  to  be  a  saturated  com 
pound.  Four  atoms  of  any  other  monad  would,  however, 
satisfy  this  condition  ;  and  we  find,  in  fact,  that  one  or  more 
of  the  four  atoms  of  hydrogen  can  be  substituted,  step  by 
step,  for  chlorine,  so  that  the  following  substitution  products 
are  obtained  : 

CH4.     CH8C1.     CHa  Cla.     CH  Cl,.     C  C14. 


Elementary  Chemistry.  229 

The  four  combining  powers  of  the  carbon  atom  can  be 
saturated  not  only  by  the  union  of  the  carbon  to  four  monad 
atoms,  but  also  by  its  union  to  two  dyad  atoms,  or  to  one 
triad  and  one  monad,  or  to  one  tetrad  atom.  Thus  in  carbon 
dioxide  (carbonic  acid),  O2  C,  and  carbon  disulphide,  S2  C, 
we  have  a  carbon  atom  saturated  with  two  dyads  ;  in  hydric 
cyanide  (prussic  acid),  HNC,  we  have  a  carbon  atom  satu 
rated  with  a  triad  (N)  and  a  monad  (H)  element. 

When  two  atoms  of  tetratomic  carbon  unite  together,  a 
new  radical  or  group  of  atoms  is  formed  ;  this  duplication  of 
the  carbon  element  takes  place  by  a  combination  of  one  of  the 
four  combining  units  of  one  atom  with  one  of  the  four  units 
of  the  other  atom  ;  so  that  two  of  the  eight  original  combi 
ning  units  are  saturated  or  disposed  of,  and  only  six  remain 
free  to  combine.  Hence,  whilst  CH4  is  the  type  of  the  mono- 
carbon  series,  C2  H6  is  that  of  the  dicarbon  series,  and  simi 
larly,  C3  H8  that  of  the  tricarbon  series  ;  and  no  compound 
of  any  of  these  three  series  is  known  containing  respectively 
more  than  four,  six,  or  eight  atoms  of  a  monad. 

Other  groups  of  bodies  exist  in  which  all  the  combining 
powers  of  the  carbon  are  not  fully  satisfied  ;  such  bodies,  for 
instance,  as  carbonic  oxide,  CO,  and  olefiant  gas,  C2  H4. 
These  substances  are  termed  non-saturated  compounds,  and 
possess  the  peculiar  property  of  uniting  directly  with  other 
elements  in  such  quantity  as  to  fill  up  the  vacant  combining 
powers.  Thus  carbonic  oxide  and  olefiant  gas  both  combine 
directly  with  C12  to  form  saturated  compounds,  which  con 
form  to  the  law  above  stated  ;  whilst,  on  the  other  hand,  we 
find  it  impossible  to  obtain  a  combination  of  chlorine  with 
CO.2,  or  with  C2  H6. 

The  following  graphical  representation  of  these  three  typi 
cal  compounds  (see  p.  230)  may  help  to  render  their  mode  of 
formation  more  evident. 

From  these  figures  it  is  seen  that  an  addition  of  C  H2  is 
necessary  to  pass  up  the  series.  This  addition  can  actually 
be  experimentally  made,  and  the  higher  and  more  complicated 
carbon  groups  thus  obtained  from  the  lowest  and  simplest 


230 


Elementary  Chemistry. 


one,  whilst  this,  in  its  turn,  can  be  prepared  from  its  con 
stituent  elements.  We  are  well  acquainted  with  no  less  than 
fifteen  of  this  series,  containing  from  one  to  fifteen  atoms  of 
carbon,  combined  with  a  saturating  quantity  of  hydrogen,  and 
each  member  of  the  series  forms  a  starting-point  for  a  num 
ber  of  peculiar  derivatives,  all  containing  a  common  constitu 
ent,  and  exhibiting  a  family  likeness. 

The  compounds  obtained  from   each   of  these  series  of 


Monocarbon  Series. 


Dicarbon  Series. 


Tricarbon  Series. 


mono-  di-  tri-  and  higher  carbon  groups,  may  indeed  be  com 
pared  with  those  of  the  inorganic  metals,  and  each  different 
carbon  series  may  be  supposed  to  contain  a  group  of  atoms  of 
carbon  and  hydrogen,  which  plays  the  same  part  in  these 
compounds  as  the  metal  does  in  the  metallic  salts,  and  to 
which  the  name  of  compound  radical  has  been  given.  The 
radical  contained  in  each  of  the  three  typical  substances  just 
mentioned  is  found  to  be  a  hydrocarbon,  containing  one 
atom  less  hydrogen  than  the  original  type,  and  each  of  these 
bodies  is  therefore  termed  the  hydride  of  a  radical,  and  con- 

TT     \ 

sidered  to  be  a  molecule  of  hydrogen  ^  v ,  in  which  one  atom 
of  the  hydrogen  is  replaced  by  a  radical ;  thus  we  have  : 


Monocarbon  Series. 

Dicarbon  Series. 

Tricarbon  Series. 

Methyl-      CH3 
Hydride        H 

Ethyl-      C2H6 
Hydride       H 

Propyl-      C3H7 
Hydride    •    fi 

Elementary  Chemistry. 


231 


By  replacing  the  one  of  hydrogen  out  of  the  radical  by  chlorine, 
we  obtain  the  corresponding  chlorides :  viz. — 


Monocarbon  Series. 

Dicarbon  Series. 

Tricarbon  Series. 

Methyl-     CH3 
Chloride      Cl 

Ethyl-     C2H5 
Chloride     Cl 

Propyl-     C3H7 
Chloride       Cl 

And  by  replacing  the  same  hydrogen  by  the  monatomic  radical 
H  O  in  each  hydride,  we  obtain  an  important  class  of  bodies 
termed  the  alcohols. 


Monocarbon  Series. 

Dicarbon  Series. 

Tricarbon  Series. 

<c 
05 

PQ 

»-4 

O 

tD 

Methyl-  CH3  )  n 
Alcohol      H   (  u 

•Ethyl-     C2H5)n 
Alcohol      H  }u 

Propyl-  C3H7  >  n 
Alcohol      H  |u 

The  molecules  of  the  radicals  methyl  CH3,  ethyl  C2  H5,  and 
propyl  C3  H7,  in  these  several  compounds  remain  indivisible 
throughout  all  the  derivatives,  and  give  the  peculiar  characters 
to  each  series. 

As  in  mineral  chemistry  we  have  radicals  (see  p.  139),  some 
of  which  are  monads,  and  some  dyads,  triads,  or  tetrads,  so 
amongst  the  carbon  compounds  some  radicals  exist  in  which 
more  than  one  combining  power  remains  unsaturated,  and 
which  therefore  act  as  polyatomic  radicals  :  thus  methylene 

ii  ii  ii 

CH2,  ethylene  C2H4,  and  propylene,  C3  H6,  are  dyads  ;  whilst 

in 
glyceryl,  C3  H5,  is  a  triad. 

These  bodies  give  rise  to  a  large  class  of  derivatives,  each 
containing  the  radical  or  group  of  carbon  and  hydrogen  atoms. 
All  the  substances  analogous  to  the  foregoing,  or  derived  from 
them,  are  classed  as  the  alcohol  group  of  organic  bodies. 
Other  carbon  compounds  are,  however,  known,  which  are 
saturated,  but  contain  the  carbon  atoms  more  intimately 
united  together,  than  the  members  of  the  alcohol  group  ;  the 


232  Elementary  Chemistry. 

principal  group  of  these  substances  is  termed  the  aromatic 
group  of  organic  bodies.  Thus,  the  formula  of  Benzol  is  C« 
H6,  and  in  this  body  eighteen  of  the  twenty-four  combining 
powers  of  the  six  atoms  of  tetratomic  carbon  are  saturated  by 
combination  of  carbon  with  carbon. 

We  shall  first  study  the  properties  and  mode  of  formation 
of  some  of  the  most  important  members  of  the  alcohol  group, 
and  then  notice  the  chief  properties  of  the  aromatic  series  of 
organic  bodies. 

It  follows  from  the  tetratomic  character  of  carbon,  that 
however  the  carbon  atoms  may  be  united  together,  the  com 
bining  powers  which  remain  unsaturated  must  be  an  even 
number ;  hence  the  sum  of  the  atoms  of  monad  or  triad 
elements  united  with  the  carbon  must  be  an  even  number, 
whilst  the  number  of  dyad  elements  is  npt  thus  restricted. 

Atomic  and  Molecular  Formula. 

We  have  already  (see  note  on  page  no)  defined  a  molecule 
to  be  the  group  of  atoms  forming  the  smallest  portion  of  a 
chemical  substance,  either  simple  or  compound,  which  can 
exist  in  the  free  state.  We  have  also  seen  that  the  molecule 
of  the  compound  gases  always  occupies  the  same  space:* 
thus  the  molecules  of  hydrochloric  acid  HC1,  of  water  H2O, 
of  ammonia  NH3,  and  of  marsh  gas  CH4,  occupy  the  same 
space,  viz.,  2  volumes  (when  H  =  i  occupies  I  volume).  In 
like  manner  the  molecules  of  the  elementary  gases  in  the  free 
state  occupy  the  same  space,  or  2  volumes  :  thus  the  molecule 

of  free  hydrogen  isyr  [• ,  that  of  oxygen  Q  >- ,  that  of  nitrogen 
N  >-,  and  that  of  sulphur  ~  r  >  whilst  that  of  phosphorus  is 
P4  (weighing  124),  of  arsenic  As4  (weighing  300)  ;  and  that  of 

*  Some  apparent  exceptions  to  this  law  must  be  noticed  ;  the  molecules  of  certain 
bodies  such  as  PCU,  SbCle,  NH4  Cl,  Hga  Ch,  &c.,  are  found  to  occupy  4  volumes. 
It  has,  however,  been  satisfactorily  proved  that  these  substances,  when  heated,  de 
compose  into  two  other  bodies ;  thus  PClo  forms  PCh  and  Cls,  NH4  Cl  forms  NHs 
and  HC1,  and  these  occupy  4  volumes  in  accordance  -with  the  law. 


Elementary  Chemistry.  233 

mercury  and  cadmium  Hg  and  Cd,  respectively  weighing  200 
and  112. 

We  may  express  chemical  decompositions  either  by  atomic 
or  by  molecular  formulae  ;  thus 

H  +  Cl  =  HC1 
is  the  atomic  expression,  whilst 

H2  +  Cla  =  2HC1 

is  the  molecular  expression  for  the  same  reaction.  In  the 
first  we  assume  a  direct  combination  of  the  elements  ;  in  the 
second  we  consider  the  reaction  as  a  replacement  of  chlorine 
for  hydrogen,  or  vice  versa;  and  in  this  way  we  are  able  to 
represent  every  case  of  chemical  action  as  a  double  decom 
position. 

Classification  of  Organic  Compounds  according  to  Types. 
We  have  already  seen  that  a  large  number  of  inorganic  sub 
stances  may  with  advantage  be  classed  together  as  being  of 
one  pattern,  or  being  capable  of  being  arranged  under  some 

TT     \ 

one  typical  form.  Thus  water,  H  (  O,  forms  the  type  of  the 
monatomic  oxides  and  hydrates,  as  ^  I  O,  and  ^  £  O,  ^  1  O, 
and  tV*  [  O  5  as  well  as  of  the  monatomic  acids  and  salts, 

as  ^°2 1  O,  and  £J°2 1  O,  &c.  ;  whilst,  by  replacement  of 
both  atoms  of  hydrogen  by  a  dyad  element,  we  obtain  the 

diatomic  oxides,  such  as  CaO,  PbO,  CuO.  Two  atoms  of 
water  must  be  taken  as  the  type  of  the  di-basic  acids,  such 
as  sulphuric  and  carbonic  acids,  possessing  two  atoms  of 


replaceable  hydrogen  ;  thus  Qn  <  rn  the     two 

OL>2    {    /-\  t»vJ    {    /~v 

H  }°'         H;°' 

atoms  of  water  being  linked  together  by  the  replacement  of 

ii 
one  atom  of  hydrogen  in  each  by  the  dyad  radicals,  SO2,  and 

ii 
CO.     In  like  manner  the  hydrates  of  the  dyad  metals  are 


234  Elementary  Chemistry. 

constructed  on  the  type  of  2  atoms  of  water,  thus  TT&  [  Oa. 
The  triad  elements  or  radicals  form  compounds  upon  the 
type  of  3  atoms  of  water  ;  thus  Boron  teroxide  is  ^>  m  [•  Os, 

in 

PO  ) 
and  tribasic  phosphoric  acid  j_j     V  O3.     In  the  same  way,  a 

very  large  number  of  organic  bodies  may  be  arranged  under 
the  types  of  i,  2,  3,  or  more  atoms  of  water,  and  thus  a  stri 
king  analogy  between  the  mineral  and  carbon  compounds  is 
exhibited.  Thus,  for  instance,  the  large  and  important  fami 
ly  of  the  monatomic  alcohols  having  the  general  formula, 
Cn  H2n  +  2O,  may  all  be  considered  as  one  molecule  of  water, 

TT       J 

TJ  [  O,  in  which  an  atom  of  hydrogen  is  replaced  by  a  monad 

radical  having  the  general  formula,  Cn  H2n+i  ;  a  series  of 
diatomic  alcohols  is  also  known  of  the  general  formula,  Cn 
H2n+2O2,  and  these  bodies  are  constituted  on  the  type  of  2 

TT        \ 

molecules  of  water,  j_j2  >  Oa,  in  which  2  atoms  of  hydro 
gen  are  replaced  by  a  dyad  radical  of  the  formula  CB  H2n ; 
whilst,  lastly,  a  series  of  triatomic  alcohols  are  known  of  the 
general  formula,  Cn  H^+jOs,  in  which  3  molecules  of  water, 

TT          J 

V  O3,  must  be  taken  as  the  type,  3  atoms  of  hydrogen 
being  replaced  by  a  triatomic  radical. 

TT     \ 

The  type  of  the  molecule  of  free  hydrogen  TT  >  is  also  one 

upon  which,  as  we  have  seen,  many  inorganic  compounds  are 

H  ) 
formed  ;  thus  Q  V  is  the  molecule  of  hydrogen  in  which  one 

atom  is  replaced  by  chlorine.  So  ^,  j- ,  and  all  the  mona 
tomic  chlorides,  iodides,  and  bromides,  may  also  be  reduced 
to  the  same  type  ;  whereas  the  diatomic  chlorides,  bromides, 
and  iodides,  such  as  Mg  C12,  Pb  C12,  are  considered  as  2 

TT        J 

molecules  of  hydrogen,    j_j3  t ,  in  which  2  of  the  atoms  are 


Elementary  Chemistry.  235 

replaced  by  I  atom  of  a  dyad  metal,  and  the  other  two  by  2 
atoms  of  a  monad  ;  and  the  aluminium  and  ferric  chlorides 
are  regarded  as  6  molecules  of  hydrogen  in  which  6  atoms 
are  replaced  by  2  of  the  triad  iron  or  aluminium,  and  6  by  6 
of  the  monad  chlorine.  This  type  is  one  which  we  shall  fre 
quently  use  in  organic  chemistry,  under  which  a  large  class 
of  carbon  compounds  can  be  classed  ;  examples  are  found  in 
the  chlorides  and  hydrides  of  the  mono-  di-  and  tri-  carbon 
series  already  mentioned. 

A  third  type  upon  whose  model  many  organic  compounds 


are  built  up  is  that  of  ammonia,  H     N.     In  mineral  chemistry 

H) 
we  know  of  at  least  three  other  bodies  belonging  to  this  type, 

H)«« 

viz.,  phosphuretted  hydrogen,  H  >-  P,  arseniuretted  hydrogen, 


KM  "i  H)    in 

H  >-  As,  and  antimoniuretted  hydrogen,  H  >  Sb.  In  the  car 
bon  compounds  we  shall  become  acquainted  with  a  numerous 
family  of  compound  ammonias,  all  of  which  are  constructed 
on  the  model  of  the  simple  inorganic  ammonia  by  replacement 
of  one  or  more  atoms  of  hydrogen  by  organic  radicals. 

Those  organic  compounds  whose  constitution  is  understood, 
may  all  be  referred  to  one  of  these  three  great  typical  forms, 
viz. : — 

HN 
| 

N, 

and  by  this  means  the  consideration  and  survey  of  the 
innumerable  carbon  compounds  is  greatly  simplified. 


J -'A  ii :  V 

UNIVERSITY    MK 

CALIPOKNIA. 


236 


Elementary  Chemistry. 


LESSON   XXVIII. 

DETERMINATION  OF  THE  COMPOSITION  OF  CARBON 
COMPOUNDS. 

i.  Organic  Analysis.  Estimation  of  Carbon  and  Hy 
drogen. 

As  all  organic  compounds  contain  carbon,  and  most  of 
them  hydrogen,  the  estimation  of  these  two  constituents 
becomes  a  matter  of  importance,  and  the  method  of  analysis 
remains  nearly  the  same  for  all  organic  substances.  It  is 
founded  upon  the  fact,  that  when  any  compound  of  carbon  is 
heated  to  redness  with  excess  of  oxygen,  it  undergoes  com 
plete  combustion,  the  carbon  being  oxidized  to  carbonic 
dioxide  (carbonic  acid),  and  the  hydrogen  to  water,  so  that  by 
weighing  the  quantity  of  these  two  products  obtained  by 
burning  a  given  weight  of  the  substance,  we  can  ascertain  the 
weight  of  carbon  and  of  hydrogen  which  the  substance  con 
tained. 

The  combustion  of  the  organic  compound  can  either  be 
made  in  a  current  of  pure  oxygen  gas,  or  by  mixing  the  body 
with  pure  copper  oxide  (Cu  O),  which  readily  parts  with  its 
oxygen  to  hydrogen  or  carbon  at  a  red  heat — in  either  method 
the  products  of  combustion  being  carefully  collected  and 
weighed.  A  weighed  quantity  (generally  about  0*3  grm.)  of 
the  solid  substance  about  to  be  analyzed  by  means  of  copper 
oxide  is  brought  into  a  combustion  tube  made  of  hard  BO- 


FIG.  .58. 


hemian  glass  (AA,  Fig.  58),  about  50  to  60  centimetres  in 


Elementary  Chemistry.  237 

length,  and  drawn  out  at  one  end  to  a  fine  point,  and  open  at 
the  other.  Before  the  introduction  of  the  substance,  a  quan 
tity  of  pure  and  perfectly  dry,  freshly-ignited,  granulated, 
copper  oxide  is  brought  into  the  tube  sufficient  to  fill  about 
one  quarter  of  its  length,  and  the  substance  is  well  mixed 
with  this  oxide  by  means  of  a  brass  wire  (B,  Fig.  58)  ;  fresh 
oxide  is  then  added,  the  brass  wire  being  well  cleaned  from 
every  possible  trace  of  the  adhering  substance,  until  the  tube 
is  nearly  filled. 

The  apparatus  intended  to  collect  the  water  produced  is 
now  attached  to  the  open  end  of  the  tube  by  means  of  a  well- 
fitting  dry  cork  :  it  consists  of  a  tube  (c),  filled  with  porous 
pieces  of  calcium  chloride,  and  accurately  weighed  ;  this 
substance  effectually  absorbs  all  the  water  and  aqueous  vapor 
formed  in  the  combustion  ;  the  carbonic  acid  passes  through 
the  tube  unabsorbed,  and  bubbles  into  a  solution  of  strong 
caustic  potash  contained  in  the  bulb  apparatus  (D),  attached 
to  the  drying  tube  by  a  well-fitting  caoutchouc  joining  (E). 
The  increase  in  weight  of  the  drying  tube  and  potash  bulbs 
gives  respectively  the  weight  of  water  and  carbonic  acid  pro 
duced. 

The  combustion  tube  is  placed  in  a  long  furnace,  so  that  it 
can  be  gradually  heated  to  redness  ;  this  is  most  readily 
effected  by  a  number  of  gas-burners  arranged  in 'line,  so  that 
each  part  of  the  tube  can  be  gradually  and  separately  heated 
(F).  A  larger  number  of  small  burners  are  placed  under  the 
part  of  the  tube  containing  the  substance,  in  order  that  the 
combustion  may  be  more  accurately  regulated.  After  the 
whole  arrangement  has  been  shown  to  be  properly  air-tight, 
the  part  of  the  tube  near  the  cork,  containing  only  pure  cop 
per  oxide,  is  heated;  and  when  a  length  of  15-20  centi 
metres  of  it  is  red-hot,  the  part  of  the  tube  containing  the 
substance  is  gently  heated,  until  bubbles  of  carbonic  acid  are 
seen  slowly  to  enter  the  potash  bulbs  ;  and  the  heat  is*  ap 
plied,  so  that  this  slow  disengagement  of  carbonic  acid  con 
tinues  until  the  whole  of  the  substance  is  burnt. 

When  the  gas  ceases  to  come  off,  the  whole  length  of  the 


238  Elementary  Chemistry. 

tube  is  strongly  heated  for  some  minutes,  and  as  soon  as  the 
potash  solution  begins  to  pass  back  into  the  bulb  nearest  the 
combustion  tube  (owing  to  absorption  of  the  carbonic  acid), 
the  drawn-out  end  of  the  tube  is  broken,  the  gas  flames  ex 
tinguished  at  that  end  of  the  furnace,  and  air  drawn  for  some 
minutes  through  the  whole  apparatus  by  sucking  with  the 
mouth  through  a  tube  placed  on  the  end  of  the  potash-bulbs. 
This  operation  is  necessary,  in  order  to  collect  in  the  potash 
the  carbonic  acid  which  still  remains  in  the  combustion-tube. 
As  soon  as  this  is  finished,  the  analysis  is  complete  with  the 
exception  of  weighing  the  drying  tube  and  potash-bulbs. 
Many  precautions  must  be  taken,  and  much  attention  to  de 
tails  must  be  paid,  in  order  to  insure  accurate  results  in  or 
ganic  analysis  ;  for  an  enumeration  of  these  the  larger 
manuals  must  be  consulted. 

If  the  substance  under  examination  is  a  liquid,  it  is  sealed 
up  in  a  small  weighed  glass  bulb  drawn  out  to  a  fine  point ; 
this  is  again  weighed,  the  point  broken  off,  and  the  bulb 
dropped  into  the  combustion  tube,  and  the  operation  con 
ducted  as  above  described.  When  nitrogen  is  contained  in 
the  body  about  to  be  analyzed,  it  is  necessary  to  place  some 
turnings  of  metallic  copper  in  the  front  part  of  the  tube  to 
decompose  any  nitrous  fumes  which  are  formed  and  would  be 
absorbed  by  the  potash,  and  thus  impair  the  result. 

Determination  of  Nitrogen.  Nitrogenous  organic  bodies, 
when  heated  with  caustic  soda,  or  potash,  yield  the  whole  of 
the  nitrogen  which  they  contain  in  the  form  of  ammonia.  This 
evolution  of  ammonia  is  easily  rendered  evident  by  heating  a 
small  piece  of  cheese  with  solid  caustic  soda.  Upon  this  re 
action  a  method  is  based  for  determining  the  quantity  of 
nitrogen  in  organic  bodies  ;  it  consists  simply  in  heating  a 
given  weight  of  substance  with  a  mixture  of  caustic  soda  and 
qui9klime  in  a  tube,  and  collecting  the  ammonia  formed,  in 
hydrochloric  acid,  and  estimating  the  weight  of  ammonium- 
chloride  produced  by  weighing  as  double  platinum  salt.  For 
every  100  parts  by  weight  of  this  salt  obtained,  the  substance 
contains  6'35  parts  of  nitrogen. 


Elementary  Chemistry.  239 

In  certain  cases,  viz.,  when  the  nitrogen  is  contained  as  an 
oxide  in  the  organic  substance,  the  foregoing  method  cannot 
be  employed,  inasmuch  as  these  oxides  are  not  completely 
converted  into  ammonia  ;  it  is  then  necessary  to  obtain  the 
nitrogen  gas  in  the  free  state  by  heating  the  substance  with  a 
mixture  of  copper  and  mercury  oxides,  and  passing  the  gases 
produced  over  metallic  copper.  All  the  nitrogen  comes  off  in 
the  gaseous  form,  and  may  be  easily  purified  by  caustic  soda 
from  the  carbonic  acid  also  evolved,  and  thus  the  volume  of 
nitrogen  obtained  can  be  accurately  measured.  From  this 
volume,  measured  under  given  circumstances  of  temperature 
and  pressure,  the  weight  of  the  nitrogen  can,  of  course,  be 
calculated. 

Chlorine,  siilphur,  and  phosphorus  exist  not  unfrequently 
in  organic  bodies,  and  have  to  be  determined  :  the  first  is 
estimated  by  heating  the  substance  to  redness  in  a  tube  con 
taining  pure  quicklime  ;  the  chlorine  forms  calcium  chloride, 
in  which,  on  solution  in  nitric  acid,  the  chlorine  is  weighed  as 
silver  salt.  Sulphur  and  phosphorus  are  determined  by  heat 
ing  the  organic  body  with  a  mixture  of  pure  nitre  and  sodium 
carbonate,  placed  in  a  tube  ;  sulphuric  and  phosphoric  acids 
are  formed  and  estimated  in  the  usual  manner. 

Oxygen  is  usually  obtained  by  difference,  that  is,  by  sub 
tracting  the  sum  of  the  weights  of  all  the  constituents  which 
have  been  directly  determined  from  the  weight  of  the  sub 
stance  taken :  several  direct  methods  for  the  estimation  of 
oxygen  have  been  proposed,  but  these  are  not  often  used. 

2.  Determination  of^  the  Composition,  Molecular  Weight, 
and  Formula  of  an  Organic  Compound. 

The  above  methods  of  analysis  give  us  the  percentage 
composition  of  the  substance,  and  the  relation  between  the 
number  of  atoms  of  carbon,  hydrogen,  oxygen,  &c.,  con 
tained  in  the  compound,  but  we  need  to  make  a  further 
determination  in  order  to  get  to  know  the  formula  and 
the  molecular  weight  of  the  body.  Thus,  in  an  analysis 
of  glacial  acetic  acid,.  0-395  grammes  of  substance  was 
found  to  yield  0-580  grammes  of  carbonic  acid,  and  0-235 


240  Elementary  Chemistry. 

grammes  of  water;  hence  100  parts  of  glacial  acetic  acid 
consist  of 

Carbon  ....  40-0 
Hydrogen  .  .  .  6*6 
Oxygen  ....  53-4  (By  difference.) 

lOO'O 

If  we  divide   these  numbers   respectively  by  the  combi- 

40  6'6 

ning  weights    of  carbon,  hydrogen,  and   oxygen, — =  3'3> — 

53*4 
=  6-6,  and  ~^-  =  3-3,  we    obtain   the   relation  between  the 

combining  weights  of  these  constituents  present.  Thus  we  see 
that  the  number  of  atoms  of  carbon  and  oxygen  is  equal, 
whilst  that  of  hydrogen  is  twice  as  large  ;  the  composition  of 
acetic  acid  is,  therefore,  represented  by  Cn  Han  On,  but  we  do 
not  know  whether  the  true  formula  is  C  Ha  O,  C3  H4  O2,  or 
C3  H6  O3  ;  or  whether  it  contains  a  still  higher  number  of 
carbon  atoms.  In  order  to  decide  this  point,  and,  therefore, 
to  determine  the  molecular  weight  of  the  substance,  we  must 
endeavor  to  find  a  compound  of  it  with  some  well-known 
element  (such  as  silver),  in  which  one  atom  of  hydrogen  in 
acetic  acid  is  replaced  by  one  atom  of  silver  ;  that  is,  we 
must  find  the  weight  of  C,  H,  and  O,  in  the  ascertained  re 
lative  proportion,  which  forms  a  compound  with  one  atom  of 
silver.  On  examination  we  find  that  only  one  such  compound 
of  silver  and  acetic  acid  exists  ;  and  we  find  by  experi 
ment  that  100  parts  of  silver  acetate  contain  64'68  parts 
by  weight  of  silver  ;  hence,  the  weight  of  the  carbon, 
hydrogen,  and  oxygen,  united  with  silver  (Ag— 108),  is 

6  -6ft~~  =  5^'9^-  *n  t*"8  silver  acetate,  however,  one 
atom  of  hydrogen  of  the  glacial  acid  was  replaced  by  one  of 
silver,  so  that  the  molecular  weight  of  the  glacial  acetic  acid 
is  found  to  be  58-98  +  1  =  5 9^98,  or  its  formula  is  : 


Elementary  Chemistry.  241 

2  C  =  24 
4H=   4 

2  O  =  32 

60 

The  slight  difference  observed  between  the  found  (59^98) 
and  the  calculated  (60)  molecular  weight  arises  from  un 
avoidable  errors  of  experiment  ;  the  more  analyses  of  the 
substance  are  made,  the  nearer  will  the  mean  result  approach 
the  calculated  numbers. 

In  a  similar  manner  the  molecular  weights  of  organic 
bases  are  determined  by  ascertaining  the  weight  of  the  sub 
stance  which  unites  with  a  known  weight  of  hydrochloric 
acid  to  form  a  salt  In  the  case  of  certain  organic  acids  and 
bases,  two  or  more  compounds  containing  different  propor 
tions  of  silver  (or  other  metal)  and  hydrochloric  (or  other 
acid)  are  known,  and  it  becomes  a  matter  for  consideration 
which  of  these  is  to  be  taken  as  containing  one  molecule  of 
the  organic  compound  to  one  atom  of  metal  or  acid ;  the 
choice  in  these  cases  is  determined  by  the  general  proper 
ties  of  all  the  compounds,  which  never  fail  to  point  out  the 
true  character  of  the  substance.  The  same  method  of  deci 
sion  also  applies  to  many  other  bodies,  such  as  sugar,  tur 
pentine,  &c.,  which  do  not  readily  enter  into  combination  with 
a  metal  or  an  acid. 

There  is  one  most  important  property  by  which  the  mole 
cular  weight  of  volatile  organic  bodies  can  be  ascertained, 
viz.,  the  density  or  specifi c  gravity  of  their  vapors.  We  have 
already  seen  that  the  vapor  volume  occupied  by  the  mole 
cule  of  almost  all  volatile  compounds  is  twice  that  occupied 
by  the  atom  of  hydrogen.  There  are  a  very  few  exceptions 
to  this  general  law,  and  these  exceptions  can  frequently  be 
explained  by  the  fact  that  the  substances  decompose  when 
heated,  a.nd  that  the  vapor  is  not  simply  that  of.  the  original 
compound.  The  molecule  of  water,  H2O,  weighing  18,  oc 
cupies  twice  as  large  a  volume  as  the  atom  of  hydrogen 

II 


242  Elementary  Chemistry. 

weighing  I,  or  the  density  of  water-gas  is  9 ;  so  hydrochloric 
acid,  HC1,  weighing  36-5,  occupies  two  volumes,  and  its  den 
sity  is  1875,  and  ammonia,  NH3,  weighing  17,  has  a  density 
of  8-5. 

This  same  simple  relation  also  holds  good  in  organic  che 
mistry.  The  molecule  of  every  volatile  organic  compound 
occupies  a  volume  twice  as  large  as  that  occupied  by  an  atom 
of  hydrogen  'weighing  I  ;  or  the  density  of  an  organic  com 
pound  is  half  its  molecular  weight. 

The  experimental  determination  of  the  vapor  densities  of 
organic  compounds  thus  becomes  an  important  matter  as 
serving  to  control  the  correctness  of  the  molecular  weight 
ascertained  by  the  foregoing  methods.  Thus,  for  instance, 
the  density  of  the  vapor  of  acetic  acid  is  found  by  experiment 
to  be  30-07  (H  =  i) ;  and  this  accordingly  gives  a  molecular 
weight  to  acetic  acid  of  60-14,  a  number  agreeing  with  that 
obtained  from  purely  chemical  considerations  (see  ante,  p.  241). 

Another  example  may  serve  to  render  evident  the  impor 
tance  of  this  relation  :  the  combustion  of  acetal  shows  that 
the  simplest  relation  of  its  constituent  atoms  is  represented 
by  the  formula  C3  H7  O  ;  *  the  determination  of  vapor  density, 
however,  gives  the  number  59-8  as  the  density  of  acetal  gas, 
hence  the  molecular  weight  of  acetal  must  be  59  x  2,  and 
its  formula  not  C3  H7  O  =  59,  but  C6  H14  O2  =  118.  It  is, 
of  course,  possible,  when  the  molecular  weight  of  a  compound 
has  been  otherwise  ascertained,  to  calculate  its  vapor  densi 
ty  ;  this  calculated  density  will  always  differ  slightly  from 
that  determined  by  experiment,  owing  to  the  unavoidable 
errors  which  occur  ;  this,  however,  does  not  detract  from  the 
value  of  this  method  of  controlling  the  molecular  formula  of 
a  substance. 

Determination  of  Vapor  Density. 
Two   methods   are   employed  for  determining  the   vapor 

*  We  see  that  as  this  formula  contains  an  uneven  number  of  hydrogen  atoms 
the  existence  of  this  substance  is  impossible  :  we  know  that  the  true  formula  must 
be  a  multiple  of  this,  which  multiple  we  decide  by  the  vapor  density. 


Elementary  Chemistry. 


243 


density  of  a  compound,  (i)  By  ascertaining  the  weight  of  a 
given  volume  of  vapor.  (2)  By  ascertaining  the  volume  of  a 
given  weight  of  vapor.  In  the  first  of  these  processes,  a  thin 
glass  globe  is  employed  of  about  200  to  300  cubic  centi 
metres  in  capacity,  having  a  finely  drawn-out  neck  ;  the 
exact  weight  of  the  globe  filled  at  a  certain  temperature  and 
under  an  observed  pressure  having  been  found,  a  small  por 
tion  of  the  substance  whose  density  is  to  be  determined  is 
brought  inside,  and  the  globe  then  heated  by  plunging  it  into 
a  water-  or  oil-bath  (Fig.  59)  raised  to  a  temperature  much 
above  the  boiling  point  of  the  substance.  As  soon  as  the 


FIG.  59. 

vapor  has  ceased  to  issue  from  the  end  of  the  neck,  this  end 
is  hermetically  sealed  before  a  blowpipe,  and  the  exact  tem 
perature  as  well  as  barometric  pressure  observed.  The  bulb 
thus  filled  with  vapor  is  allowed  to  cool,  and  is  next  accurate 
ly  weighed,  and  the  point  of  the  neck  broken  under  mercury  ; 
the  mercury  rushes  into  the  globe,  owing  to  the  vapor  being 
condensed,  and,  if  the  experiment  has  been  well  conducted, 
completely  fills  it.  From  the  volume  of  mercury  which  thus 
enters,  the  capacity  of  the  globe  is  obtained. 

We  have  now  all  the  data  necessary  for  the  determination. 
In  the  first  place  we  have  to  find  the  weight  of  a  given  volume 
of  the  vapor  under  certain  circumstances  of  temperature  and 


244  Elementary  Chemistry. 

pressure,  and  we  then  have  to  compare  this  with  the  weight 
of  an  equal  volume  of  hydrogen  gas  measured  under  the 
same  circumstances.  The  following  example  of  the  vapor 
density  of  volatile  hydro-carbon  may  serve  to  illustrate  the 
method;  weight  of  globe  filled  with  dry  air  at  15*5°  23*449 
grammes;  weight  of  globe  filled  with  vapor  at  110°  23720 
grammes  ;  capacity  of  the  globe  178  cbc.  As  the  barometric 
column  stood  near  to  760  mm.  and  underwent  no  change  from 
the  beginning  to  the  end  of  the  experiment,  no  correction  for 
pressure  is  necessary.  In  order  to  get  the  weight  of  the  vacuous 
globe,  the  weight  of  air  contained  must  be  deducted  from  the 
weight  of  globe  in  air.  Now  I  cbc.  of  air  at  o°,  and  760  mm. 
weighs  0*001293  gramme,  and  178  cbc.  of  air  at  15*5  would 

occupy  I782*  273-=  168-4  at  o°,  and  the  weight  of  this  air 

is  0-2 1 8  gramme  :  hence  the  weight  of  the  vacuous  bulb  is 
23-231,  and  the  weight  of  vapor  23-720 — 23-231  =  0-489 
gramme.  We  must  now  find  what  178  cbc.  of  hydrogen  at 
110°  will  weigh  :  1,000  cbc.  of  hydrogen  at  o°  weigh  0-08936 
gramme  ;  178  cbc.  will  contract  to  126-9  CDC-  at  o°.  126  cbc. 
of  hydrogen  at  o°  weigh  0-01134  gramme,  and  this  is  there 
fore  the  weight  of  178  cbc.  of  hydrogen  at  110°.  Hence 

°4  9  ,  =  43-13  'is  the  density  of  the  vapor,   as  found  by 
0*01134 

experiment.  The  formula  of  the  substance  is  Ce  Hu,  or  its 
molecular  weight  is  86.  In  this  example  many  minor  correc 
tions,  such  as  the  expansion  of  the  glass  globe,  the  error  of 
the  mercurial  thermometer,  &c.,  are  not  considered  ;  the 
above  method  gives  results  which  are  sufficiently  accurate 
when  the  object  is  to  control  the  molecular  weight  of  a 
compound. 

The  second  method  of  vapor  density  determination  con 
sists  in  ascertaining  the  volume  occupied  by  a  given  weight 
of  substance  when  heated  up  to  a  temperature  considerably 
above  its  boiling  point.  The  mode  of  calculation  is  in  princi 
ple  the  same  as  that  of  the  former  method.  For  the  details 
of  manipulation  the  reader  must  refer  to  the  larger  manuals. 


Elementary  Chemistry. 


245 


Boiling  Point. 

Another  important  physical  property  of  organic  compounds 
is  the  boiling  point.  Every  volatile  chemical  compound  has, 
under  given  circumstances  of  pressure,  a  fixed  and  constant 
boiling  point ;  and  this  property  is  useful  in  ascertaining  the 
purity  of  an  organic  liquid,  as  well  as  enabling  us  to  separate 
the  constituents  of  a  mixture  by  means  of  fractional  or  con 
tinued  distillation.  The  boiling  points  of  the  homologous 
series  of  hydrides,  alcohols,  chlorides,  &c.  (p.  231),  rises  with 
the  increase  of  carbon,  and  frequently  proportionally  to  this 
increase,  although  no  general  law  connecting  boiling  point 
and  chemical  composition  can  be  expressed.  The  arrange 
ment  used  in  the  separation  of  liquids  boiling  at  different 
points  by  means  of  fractional  distillation  is  represented  in 
Fig.  60.  The  large  surface  presented  by  the  bulb  tube  (a) 
allows  the  vapor  of  the  less  volatile  constituents  to  condense 


FIG.  60. 


and  flow  back  into  the  flask  containing  the  mixture  ;  the 
temperature  of  the  vapor  is  indicated  by  the  thermometer  (3), 
and  when  the  temperature  rises  beyond  a  given  point  the 
liquid  already  distilled  over  is  removed  and  an  empty  flask 
substituted  to  collect  the  portion  of  liquid  next  coming  over. 


246  Elementary  Chemistry. 


LESSON  XXIX. 

MrjNATOMic  ALCOHOL  GROUP. 

General  Characteristics.  The  monatomic  alcohols  and  their 
derivatives  form  a  very  large  and  important  group  of  organic 
compounds.  As  an  example  of  these  alcohols  we  may  take 
ethyl  alcohol,  C3  H6  O,  known  as  spirits  of  wine  ;  this  sub 
stance,  in  common  with  all  the  other  alcohols  of  this  series, 
may  be  considered  as  water  in  which  one  atom  of  hydrogen 
is  replaced  by  a  radical  having  in  this  case  the  formula  C2  H6  ; 

f    T-T     ) 

hence  ethyl  alcohol  is     2  £j5  \    O.     Ethyl  alcohol  is  in  consti 
tution  analogous  to  caustic  potash,        t-  O  ;  and  as,  by  adding 


hydrochloric  acid  to  the  latter,  we  get  KC1  (potassium  chloride) 

TT      -\ 

and  j_[  >•  O,  so  by  bringing  alcohol  in  contact  with  this  acid 

TT    -\ 

we  get  C2H5  Cl  (ethyl  chloride),  and  -     >  O  ;    in    like  manner 


the  chlorides,  iodides,  and  bromides  of  all  the  alcohol  radicals 
can  be  obtained.  The  analogy  of  the  ethyl  with  the  potas 
sium  compounds  is  still  further  seen  in  the  fact  that  an  ethyl 
compound  exists  which  stands  to  alcohol  in  the  same  relation 
as  potassium  monoxide  to  caustic  potash  ;  this  compound  is 

f  T-T     ") 

common-  or  ethyl-ether,    QJjj6   [•  O.     We   also   have  analo 

gous  compounds  to  the  potassium  salts  ;  thus  we  have,  potas 
sium  nitrate,  N^  j  O,  ethyl  nitrate,  ^J^5  J-  O, 

K     ) 

ii 

Hydric-potassium-sulphate  SO2  f  Oa  J 

H     ) 
C,H.  I 

Hydric-ethyl  sulphate     .     SO«  f  O2  ; 

H    ) 
Potassium  acetate  .    .    C2^s°  |  O  ; 


Elementary  Chemistry.  247 

Ethyl  acetate     .     .     .  £*  ^  °  J  O. 

If  ethyl  alcohol  be  exposed  to  oxidizing  agents,  it  first  loses 
2  atoms  of  hydrogen,  and  is  converted  into  a  new  substance, 
C3  H4  O,  called  ethyl  aldehyde  ;  and  if  the  oxidizing  action 
continues  longer,  another  product  termed  acetic  acid  is  formed, 
which  has  the  composition  C2H4O2.  Both  these  substances 
may  be  regarded  as  containing  an  oxidized  radical,  or  ethyl  in 
which  2  atoms  of  hydrogen  are  replaced  by  I  atom  of  oxygen  ; 
aldehyde  thus  becomes  the  hydride  of  this  radical  (called 


Acetyl),  CaH3O  |  f  whilst  acetic  acid  is  water  in  which  I 
atom  of  hydrogen  is  replaced  by  acetyl  :  thus,  2  SH  >•  O. 

Aldehyde  can  be  reduced  again  to  alcohol  directly  by  addition 
of  2  atoms  of  hydrogen,  but  acetic  acid  cannot  be  directly 
reduced  to  alcohol. 

Every  alcohol  can  thus  be  oxidized,  and  yields  an  aldehyde 
and  an  acid  which  stand  in  the  same  relation  to  one  another 
as  the  above-mentioned  bodies.  All  these  acids  are  mono 
basic  ;  that  is,  they  contain  only  I  atom  of  hydrogen  replace 
able  by  a  metal.  This  hydrogen  can  also  be  replaced,  not 
only  by  the  ethyl  and  the  other  alcohol  radicals,  giving  rise  to 

bodies  called  the  compound  ethers,  of  which,    £2jj3       [•  O, 

acetic  ether  or  ethyl-acetate,  may  be  taken  as  an  example,  but 
also  by  acetyl  itself  or  the  other  oxidized  radicals  ;  thus  we 

(~*  T~T  O  ) 
obtain  ^'-ur3r\  >  O,  a  substance  which  we  shall  term  acetyl 


acetate,  but  which  is  frequently  called  acetic  anhydride,  or 
even  anhydrous  acetic  acid. 

Each  alcohol  also  forms  a  series  of  compound  ammonias  ; 

H) 

that  is,  ammonia,  H  >•  N,  in  which  one  or  more  atoms  of  hydro- 

H) 
gen  are  replaced  by  a  radical  :  thus,  for  the  ethyl  series  we 


248  Elementary  Chemistry. 

C*H^  C2H5 

have  ethylamine      H   >•  N  ;  diethylamine.  C2H5  >  N  ;        and 

H  )  H 

C2H6) 
triethylamine,  C2  H6  >•  N.      We    can,   indeed,   go    one    step 

C2H5) 

further  in  the  addition  of  ethyl,  and  obtain  a  caustic  substance 
resembling  potash  in  its  properties,   and  analogous   to   the 

ammonium  hydrate,      ^  (•  O,  but  containing  4  of  ethyl   in 

place  of  the  4  of  hydrogen  ;  thus,  N(C2H5)*  1    Q  ;  to  this  sub 

stance  the  name  of  tetra-ethyl-ammonium  hydrate  is  given. 

Compound  ammonias  are  also  known  in  which  one  or  more 
atoms  of  the  hydrogen  of  ammonia  is  replaced  by  the  oxygen 
ized  radical  of  the  acids,  and  these  compounds  are  termed 
Amides  ;  thus  we  have  with  acetyl, 

C2H3O)  CaH.Cn 

acetamide,      H       >  N  ;  diacetamide,  C2H3O  >  N  ; 


. 

C2H3O 
and  ethyl-diacetamide,C2H3O  >•  N. 

C2HB 

Compounds  of  the  alcohol  radicals  analogous  to  arsenic  and 
phosphorus  trihydrides  are  also  known  ;  thus,  for  instance, 
CH3^  C2H6) 

C  H3  >-  As,  trimethyl-arsine  ;  and,  C2  H5  >-  P,  triethyl-phos- 
CH3^  C2H5) 

phine,  are  -known.  The  alcohol  radicals  likewise  combine 
with  metals,  such  as  zinc,  tin,  &c.,  to  form  bodies  which  in 
their  turn  combine  with  chlorine,  &c.,  and  have,  therefore, 
been  termed  the  organo-metallic  radicals  ;  such  substances 

are  zinc  ethyl,  £2  ^5  1  Zn,  and  cacodyl,  (C  H3)2  As. 

v—  2      -Ti  6  j 

The  following  is  a  complete  list  of  all  the  monatomic  alco 
hols  and  acids  now  known,  giving  their  formulas,  and  boiling 
and  melting  points.  In  some  cases  the  alcohol  correspond 
ing  to  a  known  acid  has  not  yet  been  obtained  ;  a  blank  is 
then  left  in  the  alcohol  series. 


Elementary  Chemistry. 


249 


I 
H 


yield 


C  ALCOHOLS 
ula  Cn  H2n  + 


w     ^      I       1  1      HH    HI    CS 

+•  +          +  + 


OO 
CO 

vr>\b    I 


060 


uuuuuuuuuuuuuuuuuuuu 


OOOOOOOO      O  O  OO 

H?  j?  J?  hJ  H?  K?  K?  *z  i  H?  i  i  h?  i    i    i    i    i  ^r  "T? 

KKWW^WhlHWIPCI  |  K  |     |    |    |    |  WW 

o  to  t-      o 

UUUUUUUU      U  U  UU 


<yu          <1> 

Q 


. 
U 


3s 


11* 


250  Elementary  Chemistry. 

MONOCARBON    OR   METHYL  SERIES. 

Radical  Methyl,  CH3.  Methyl  alcohol,  ™8  j  O,  com 
monly  called  wood-spirit.  It  occurs  in  the  dry  distillation  of 
wood,  forming  about  one  per  cent,  of  the  aqueous  distillate  ; 
it  is  likewise  met  with  in  the  oil  of  winter-green,  derived  from 
the  Gaultheria  procumbens.  Methyl  alcohol  can  likewise  be 
synthetically  built  up  from  its  constituent  elements,  but  only 
by  means  of  several  complicated  reactions,  which  will  after 
wards  be  mentioned. 

Pure  methyl  alcohol  is  obtained  from  crude  wood-spirit,  in 
which  it  is  contained  mixed  with  a  variety  of  other  organic 
compounds,  by  forming  a  crystalline  methyl  oxalate  ;  this,  on 
treatment  with  water,  is  decomposed,  and  yields  the  alcohol 
in  the  pure  state.  Methyl  alcohol  is  a  colorless,  mobile  li 
quid,  possessing  a  pure  spirituous  smell  ;  the  specific  gravity 
of  the  liquid  is  0*8142  at  o°,  and  its  boiling  point  is  66°.  It 
burns  with  a  non-luminous  flame,  and  is  soluble  in  and  mis- 
cible  with  water.  Potassium  dissolves  in  methyl  alcohol 
with  evolution  of  hydrogen  and  formation  of  potassium  me- 
thylate,  CH3  )  Q  Methyl  alcohol,  when  acted  on  by  oxidiz 
ing  agents,  yields  formic  acid  ;  no  aldehyde  of  this  series  is 
known.  By  the  action  of  bleaching  powder  on  methyl  alco 
hol,  chloroform  is  obtained  ;  acted  upon  by  hydrochloric 
acid,  the  alcohol  yields  methyl  chloride. 

The  action  of  strong  sulphuric  acid  on  methyl  alcohol  is 
remarkable,  and  is  the  type  of  a  general  reaction.  These 
two  substances  must  be  mixed  with  care,  as  great  heat  is 
evolved  when  they  come  in  contact.  The  first  substance 

formed  is  hydric  methyl-sulphate,  CQ    \      »  by  exchange  of 

H  ;  ° 

hydrogen  for  methyl.     When  this   body  comes   in  contact 
with  another  molecule   of  alcohol,    we    have    another    ex- 


Elementary  Chemistry.  251 

change  of   hydrogen  and    methyl   occurring  ;    but  as   this 
exchange    can    occur    in     two    directions,    we    get    either 

H      )  H  ^)  CH3  ) 

m   }  I  -  **  I 

^s  (  O  and  ~"      I  O2,  or        V  O  and  ~%     V  Oa  :    in    the 

CHa  {  ^O2     |  TT    f  oUa    f 

H     )  ~XJ  CH3J 

first  case,   methyl   ether   and    sulphuric  acid ;   and  in    the 
second,  water  and  di-methyl  sulphate. 

Methyl  Chloride,  CH3  Cl,  is  obtained  as  a  colorless  gas, 
condensing  at  -20°,  by  acting  upon  methyl  alcohol  with 
hydrochloric  acid  or  phosphoric  penta-chloride  ;  it  is  also 
formed  along  with  other  substances  by  the  action  of  chlorine 
upon  marsh  gas.  The  bromide  and  iodide  are  colorless 
liquids,  prepared  by  acting  on  methyl  alcohol  with  bromine 
and  iodine  in  presence  of  phosphorus. 

Methyl  Hydride.  Marsh  gas,  CH3  H.  As  we  have  seen, 
this  gas  occurs  in  nature  as  fire-damp  and  the  gas  of  marshes. 
It  can  be  obtained  easily  by  heating  sodium  acetate  with 
caustic  alkali  ;  the  acetic  acid  splitting  up  into  carbonic 
dioxide  and  marsh  gas,  C2  H4  Oa.=  CO2  +  CH4.  Methyl 
hydride  can  also  be  obtained  by  passing  the  vapor  of  carbon 
disulphide,  together  with  sulphuretted  hydrogen  gas,  through 
a  red-hot  tube,  and  in  this  way  it  may  be  built  up  from  its 
constituent  elements.  It  may  likewise  be  obtained  by  heat 
ing  methyl  iodide  together  with  zinc  and  water.  Methyl 
hydride  is  a  colorless  inflammable  gas,  which  burns  with  a 
slightly  luminous  flame,  and  when  mixed  with  air  produces  a 
dangerously  explosive  gas.  Most  oxidizing  reagents  do  not 
act  upon  this  hydride,  but  chlorine  attacks  it  in  the  presence 
of  sunlight  with  such  violence,  as  to  produce  an  explosion. 
By  the  slow  action  of  chlorine,  several  substitittion  products 
are  formed,  amongst  the  chief  of  which  are — methyl  chloride, 
CH3  Cl,  chloroform,  CH  C13,  and  carbon  tetra-chloride,  C 
C14. 

Chloroform,  CH  C13,  is  formed  by  the  action  of  chlorine  on 
marsh  gas,  but  it  is  prepared  by  acting  upon  methyl  or  ethyl 
alcohols  with  bleaching  powder.  It  is  a  mobile,  heavy  liquid, 


252  Elementary  Chemistry. 

possessing  a  powerful  and  agreeable  smell ;  its  specific  gravity 
is  i  -525  at  o°,  and  it  boils  at  62°.  Chloroform  is  much  used 
in  medicine,  producing,  when  it  is  inhaled,  a  temporary  but 
perfect  insensibility  to  pain,  and  is  therefore  much  valued  in 
surgical  operations.  Many  other  organic  volatile  bodies  act 
in  a  similar  manner,  but  none  so  effectually  and  so  harmlessly 
as  chloroform.  An  iodine  compound,  analogous  to  the  pre 
ceding,  has  been  prepared ;  it  is  termed  lodoform,  and  is  a 
yellow  solid  body. 

Carbon  Tetra  Chloride,  C  C14,  is  a  colorless  liquid,  boiling 
at  77°,  obtained  as  the  last  product  of  the  action  of  chlorine 
on  marsh  gas.  When  this  substance  is  brought  into  contact 
with  an  amalgam  of  sodium  and  water,  an  opposite  substitu 
tion  of  hydrogen  for  chlorine  occurs,  marsh  gas  and  all  the 
intermediate  products  being  formed. 

C"T-T    ") 
Methyl  Ether,  ^^3  j-  O,  a  colorless   and   sweet-smelling 

gas  at  the  ordinary  temperature  of  the  air  ;  but  condensing  at 
—21°  to  a  colorless  liquid.  It  is  prepared  by  heating  the 
alcohol  with  sulphuric  acid,  as  already  described. 

Methyl  Cyanide,  C  H/CN  or  C2  H3  N,  is  obtained  by  the 
distillation  of  ammonium  acetate  ;  thus, 

C2  H3  (NH4)  O2  -  H4  02  =  C2  H3  N ; 

or  by  heating  potassium  methyl-sulphate  with  potassium 
cyanide.  It  is  a  colorless  liquid,  possessing  a  disagreeable 
smell,  and  boiling  at  77°.  It  is  transformed  into  ethylamine 
in  contact  with  zinc  and  dilute  sulphuric  acid,  C2  H3  N  + 

C*    TT     *) 
H4  =      '  j_j6  [•  N  ;    whilst  acted  upon  by  potash  it  forms 

acetic  acid  (see  p.  274.) 

Methyl  (Ethyl Hydride),  C2  H6.  This  substance  is  obtained, 
ist,  by  the  action  of  methyl  iodide  upon  zinc  ;  2ndly,  by  the 
decomposition  of  potassium  acetate  by  a  galvanic  current ;  and 
3dly,  by  the  action  of  barium  dioxide  on  acetic  anhydride,  thus  : 

K?  HS  0  |  °)  +  Ba  °9  =  2  (CaHs  °2)  Ba  +  Ca  Ho  +  2  C  02 

Ace''c  anhydride  and  barhim  )    •  , ,  (  Barium  acetate  and  methyl   and  carbonic 
dioxide  j  y        (  acid. 


Elementary  Chemistry.  253 

This  hydrocarbon  was  formerly  supposed  to  be  the  free 
radical  of  the  methyl  group,  but  no  methyl  compounds  have 
in  any  way  been  derived  from  it,  whilst  by  the  action  of 
chlorine  upon  it,  ethyl  chloride,  C2  H5  Cl,  is  obtained  as  the 
first  substitution  product  Hence  we  must  regard  methyl- 
and  ethyl-hydride  as  identical.  .The  nitrate,  nitrite,  cyanate, 
and  sulphate  of  the  methyl  series  are  also  known. 


LESSON   XXX. 

DI-CARBON  OR  ETHYL  SERIES. 

The  starting  point  of  this  important  series  is  common — or 
ethyl-alcohol,  C2  H6O  ;  this  is  the  ethyl  hydrate,  and,  like  its 
numerous  derivatives,  contains  the  radical  ethyl,  C2  H5. 

Ethyl  Alcohol,  Vr  5  [•  O,  is  obtained  in  the  vinous  fer 
mentation  of  sugar,  a  decomposition  effected  in  aqueous  sugar 
solutions  in  presence  of  yeast,  in  which  alcohol  and  carbonic 
acid  are  chiefly  formed  ;  the  other  products  of  fermentation 
are  described  under  sugar  (on  p.  308).  Alcohol  can  also  be 
prepared  from  its  elements  by  synthesis.  This  is  done  by 
obtaining  acetylene  (page  228),  and  combining  this  directly 
with  hydrogen  to  form  olefiant  gas,  C2  H4  ;  this  substance 
combines  directly  with  strong  sulphuric  acid,  forming  hydric 

ethyl-sulphate,  C2  H5  )  Q 
ii     | 

S02jQ 

H  ;° 

and  this,  when  boiled  with  water,  forms  sulphuric  acid  and 
alcohol  by  exchange  of  ethyl  for  hydrogen,  thus  : 


C2H6 

S02 
H 


H 


II 


OH 


O          H  \  2  J.  O 


C2 


SO2  )  ^  H 


254  Elementary  Chemistry. 

or,  hydric  ethyl-sulphate  and  water,  yield  sulphuric  acid  and 
alcohol. 

Olefiant  gas  also  combines  with  hydric  iodide  to  form  ethyl 
iodide,  which  forms  alcohol  when  heated  with  caustic  potash. 

Alcohol  and  alcoholic  liquids  are  prepared  in  large  quan 
tities  by  the  fermentation,  of  sugar  derived  from  various 
sources.  The  fermented  liquid  is  distilled,  and  the  dilute 
aqueous  spirit  thus  separated  from  non-volatile  impurities  ; 
it  is  obtained  in  a  more  concentrated  form  by  repeated  rectifi 
cations,  as  it  boils  at  a  lower  temperature  than  water.  Alcohol 
cannot,  however,  be  completely  separated  from  water  by  simple 
distillation,  the  strongest  spirit  which  can  thus  be  prepared 
containing  10  per  cent,  of  water.  To  withdraw  all  the  water, 
the  spirit  must  be  distilled  with  some  substance  capable  of 
combining  with  water,  such  as  potassium  carbonate  or  quick 
lime.  The  pure  liquid  thus  obtained  is  termed  absolute  alcohol : 
it  is  a  colorless,  mobile  liquid,  possessing  a  pleasant,  spirituous 
smell  and  burning  taste  ;  its  specific  gravity  at  o°  is  0^8095, 
and  at  I5°*5,  07939  ;  and  it  boils  at  78°vj.,  when  the  barometer 
stands  at  760  mms.  It  has  not  been  solidified,  becoming 
only  viscid  at  a  temperature  of  -100°.  Alcohol  is  very  inflam 
mable,  burning  with  a  slightly  luminous  blue  flame.  It  absorbs 
moisture  with  great  avidity,  and  mixes  with  water  in  all  pro 
portions,  the  mixture  evolving  heat  and  undergoing  contrac 
tion. 

Many  salts,  as  well  as  gases,  dissolve  in  alcohol ;  it  like 
wise  acts  as  a  solvent  for  resins,  organic  bases,  and  essential 
oils,  many  of  which  do  not  dissolve  in  water.  The  determi 
nation  of  the  strength  of  spirit,  when  free  from  sugar  or  other 
soluble  matters,  is  ascertained  by  determining  the  specific 
gravity  by  means  of  delicate  hydrometers,  and  reference  to 
accurate  tables,  showing  the  percentage  of  water.  In  these 
estimations  the  temperature  must  be  accurately  observed, 
and  corrections  for  deviations  must  be  made,  as  alcohol 
expands  considerably  with  increase  of  temperature,  and  the 
specific  gravity  is  thereby  altered.  The  "proof  spirit"  of 
the  Excise  contains  50^8  parts  by  weight  of  alcohol  to  49*2  of 


Elementary  Chemistry.  255 

water,  and  possesses  a  specific  gravity  of  0-920  at  15° -5. 
Owing  to  the  high  duty  on  pure  spirit,  the  Government  allows 
the  sale  of  a  mixture  of  ninety  parts  of  strong  alcohol  with 
ten  parts  of  wood-spirit  for  manufacturing  and  scientific  pur 
poses  ;  this  substance  is  called  "  methylated  spirit,"  and 
is  most  useful  to  the  scientific  and  manufacturing  chemist. 
Spirits,  wines,  and  beer  also  contain  more  or  less  alcohol, 
flavored  with  certain  essential  oils,  sugar,  9t  extracts. 
Brandy,  whisky,  and  the  other  spirits,  contain  from  40  to  50 
per  cent,  of  alcohol;  wines  from  17  (Madeira  and  port)  to  7 
or  8  (light  claret  and  hock)  per  cent.,  whilst  strong  ale  and 
porter  contain  from  6  to  8  per  cent 

Alcohol  is  decomposed  when  its  vapor  is  passed  through  a 
red-hot  tube  ;  hydrogen,  marsh  gas,  olefiant  gas,  naphthaline, 
benzole,  and  other  products  being  formed.  By  oxidation 
alcohol  is  transformed  first  into  aldehyde  and  then  into  acetic 
acid.  This  oxidation  may  be  effected  by  the  atmospheric 
oxygen  in  presence  of  finely  divided  platinum,  or  more  slowly 
when  certain  fermentable  bodies  are  present  (see  acetic  acid, 
p.  274).  The  alkaline  metals  attack  alcohol  with  rapidity, 
evolving  hydrogen,  and  forming  potassium  or  sodium  ethylate, 

f .    T-f     ) 

jW2         V   O.      Hydrochloric  acid  forms,   with  alcohol,   ethyl 

chloride  and  water,  and  the  corresponding  bromine  and  iodine 
compounds  act  similarly.  Strong  sulphuric  acid  combines 
with  alcohol  to  form  hydric  ethyl-sulphate,  or  sulphovinic 
acid,  a  substance  which  forms  salts  called  the  ethyl-sulphates  ; 


C2H5 


thus  potassium-ethyl-sulphate  is  SO2 


K 

Ether,  or  Ethyl-Ether,   Sa  ^5  \  O.     This  important  sub- 


stance  is  formed  in  a  variety  of  ways  from  ethyl  compounds. 
The  most  simple  reaction  by  which  ether  can  be  prepared  is 


256  Elementary  Chemistry. 

that  of  acting  upon  potassium  ethylate  with  ethyl  iodide,  an 
exchange  of  ethyl  and  potassium  taking  place,  thus  : 

C2  H5  I    +    C2H5  )    Q    .  .    „  T          C2  H5  )    n 
K    j-   (  K  J    +    C2  H5  \   °' 

Ethyl  iodide  and  potassium  ethylate  give  potassium  iodide 
and  ether. 

Another^reaction  by  which  ether  is  prepared  on  the  large 
scale  consists  in  heating  a  mixture  of  alcohol  and  sulphuric 
acid  to  140°,  when  ether  and  water  are  given  o/F.  The  decom 
positions  which  here  take  place  are  as  follows  :  in  the  first 
place,  alcohol  and  sulphuric  acid  form  hydric  ethyl- sulphate 
(sulphovinic  acid)  and  water,  by  an  exchange  of  hydrogen  and 
ethyl,  thus  : 

Hydric  Ethyl 
Alcohol.  Sulphuric  Acid.          "Water.  Sulphate. 


H 


C2  H5 


H    f    +      S02 
H 


O  C»  H'  I  O. 


H 


O 


H.) 

"     ) 


Hfv   r  S02 

H 


O. 


This  hydric  ethyl-sulphate  next  comes  in  contact  with  a 
second  molecule  of  alcohol,  another  exchange  of  hydrogen  for 
ethyl  occurs,  and  ether  and  sulphuric  acid  are  formed. 

Alcohol      and     Hydric  Ethyl         yield    Ether    and    Sulphuric 
Sulphate  Acid. 

C2H5)Q  H 

c,  H5  0        „    \  °  _  CSH.  )         „ 


Hi  S02      n  -  C2H5  f  SO2 

H     \°  O. 

The  water  formed  by  the  first  decomposition,  and  the  ether 
produced  by  the  second,  are  given  off  as  vapor,  whilst  the 
sulphuric  acid  remains  behind,  ready  again  to  go  through  the 
same  series  of  changes  on  meeting  with  two  other  molecules 
of  alcohol.  This  process  is  called  the  continuous  etherification 
process,  as  a  current  of  alcohol  may  be  passed  continuously 
through  the  sulphuric  acid  heated  to  140°,  and  a  regular  sup 
ply  of  ether  and  water  thus  obtained. 


Elementary  Chemistry.  257 

Ether  is  a  colorless,  very  mobile  liquid,  possessing  a  strong 
and  peculiar  etherial  smell.  It  is  lighter  than  water,  specific 
gravity  0736,  and  is  not  miscible  with  this  liquid.  Ether 
boils  at  34° '5,  and  its  vapor  is  37  times  heavier  than  hydro 
gen,  and  can  be  poured  from  vessel  to  vessel  like  carbonic 
acid  gas.  It  burns  with  a  luminous  flame,  and  explodes 
when  mixed  with  air.  From  its  low  boiling  point  great  care 
must  be  taken  to  avoid  explosions  when  working  with  this 
substance,  owing  to  the  vapor  becoming  mixed  with  air. 
Ether  is  easily  attacked  by  oxidizing  agents,  yielding  the 
same  products  as  alcohol,  and  it  is  also  acted  upon  by  chlo 
rine,  and  a  large  number  of  substitution  products  formed. 

Mixed  Ethers  containing  two  different  radicals  are  ob 
tained  by  acting,  for  instance,  with  ethyl-iodide  upon  potas 
sium  methylate,  thus  : 

Ethyl  Iodide       and         Potassium        •  , ,  Potassium  and  Methyl-Ethvl- 
Methylate      yield     Iodide  Ether.   ' 

Ca  H6 1       +         C  H8  \  n          v  T  C 

K        f°          KI    +    C2 

CH3 

or  by  acting  on  hydric  methyl-sulphate,  SO2  [•  O3,  with  ethyl 


alcohol.     The  following  is  a  list  of  some  of  the  more  impor 
tant  simple  and  mixed  ethers  of  this  series  : 


Table  of  Simple  and  Mixed  Ethers.  Boiling 

Point. 

Methyl  Ether    .    .    .     C2   H8   O        c   Ha'   1°    '     '~2I° 

Methyl-ethyl  Ether    ,     C3    H8   O         £   3°   \  O    .     .  +"' 

v-2  rls    ) 

Ethyl  Ether .    .    .    .     C4   H10  O        £j  g|  JO..      34° 
Methyl-amyl  Ether     .     C6   H14  O         C.  H!I  I  °    '     '      92' 


258  Elementary  Chemistry. 

Ethyl-butyl  Ether  .    .     C6   H14  O        c!  H!  1  °  '  '  8o° 

Ethyl-amyl  Ether  .     .     C7    Hlfl  O         Q  Hn  1  °  '  '  II2° 

Butyl  Ether.     .     .     .     C8   H18  O         Q!  H!  1  ^  '  I04° 

Ethyl-hexyl  Ether      .     C8  H  i8  O         £°  ^  i  O  .  .  132° 

Amyl  Ether  .     .     .     .     C10  H22  O         £5  ^J11  I  O  .  .  176° 

V-6   -Till   ) 

Ethyl  Chloride,  C2  H6  Cl,  is  obtained  as  a  mobile  liquid, 
having  an  etherial  penetrating  smell,  by  saturating  alcohol 
with  hydrochloric  acid  gas,  or  by  acting  with  the  phosphoric 
chlorides  upon  alcohol.  On  heating  the  mixture  a  volatile 
liquid  is  given  off,  which  must  be  condensed  in  a  freezing 
mixture.  Ethyl  chloride  boils  at  11°.  Ethyl  iodide,  C2  H6  I, 
and  ethyl  bromide,  C2  H5  Br,  are  obtained  by  acting  upon 
alcohol  with  iodine  and  bromine  in  presence  of  phosphorus. 
The  iodide  is  much  used  for  the  preparation  of  other  ethyl 
compounds,  owing  to  the  facility  with  which  the  iodine  can  be 
exchanged  in  double  decompositions.  It  is  a  heavy,  color 
less  liquid,  boiling  at  72^2,  and  having  a  specific  gravity  of 
1-946  at  16  . 

Ethyl  Cyanide,  C2  H5  C  N,  is  prepared  by  heating  potas 
sium  ethyl  sulphate  with  potassium  cyanide.  It  may  be  con 
sidered  as  a  nitrogen  compound  (nitril)  of  the  next  higher 
carbon  series  (propyl),  as  on  heating  with  potash  it  yields 
propionic  acid,  thus : 

Propionitril    and         Water    yield    Propionic  Acid  and  Ammonia. 

C8H6N     +       2H20   =      C3H6O2     +     NH3. 
Propionitril,  when  acted  upon  by  hydrogen,  yields  propyl- 
amine  ;  C3  H6  C  N  +  2  H2  =  T*H'  (  N.      This  reaction   is 

impor^nt,  as  it  is  one  which  is  common  to  all  the  series  of 
alcoholic  cyanides,  and  enables  us  to  pass  from  a  lower  to  a 


Elementary  Chemistry.  259 

higher  carbon  series  —  in  this  case  from  the  2  to  the  3  carbon 
series. 

Ethyl  Hydride,  C2  H6  H.  This  substance,  already  de 
scribed  as  methyl,  is  a  colorless  and  tasteless  gas,  obtained  by 
the  action  of  zinc  and  water  upon  ethyl  iodide  when  heated  to 
150°  in  a  closed  tube.  It  occurs  in  American  petroleum.  It 
is  rapidly  acted  on  by  chlorine,  and  yields  ethyl  chloride, 
together  with  a  series  of  further  substitution  products,  the  last 
of  which  is  carbon  chloride,  C2  C18. 

Ethyl  Nitrite,  C2  H5  N  O2,  is  obtained  as  a  sweet-smelling 
liquid  by  acting  upon  alcohol  with  nitric  acid,  and  it  is  con 
tained  in  the  "sweet  spirits  of  nitre"  of  the  Pharmacopeia. 

Ethyl  Nitrate,  1  O,  is  only  formed  by  the  action  of 


nitric  acid  on  alcohol  when  urea  is  present,  as  this  body 
immediately  destroys  any  nitrous  acid  which  may  be  formed, 
which  would  prevent  the  production  of  nitrate. 

f*    TT     J 

Ethyl  Sulphydrate,          ;5  >  S.     This  compound,  known  as 

Mercaptan,  is  sulphur  alcohol,  /'.  e.  alcohol  in  which  the  oxygen 
is  replaced  by  sulphur.  It  is  obtained  by  acting  on  potas- 

sium-sulph-hydrate,  ^  t  S,   with   ethyl    chloride,   ethyl    and 

potassium  changing  places.  Mercaptan,  like  alcohol,  can 
exchange  its  typical  atom  of  hydrogen  for  metals  :  it  forms 
with  mercury  an  insoluble  Compound.  This  body  boils  at  36°, 
and  possesses  the  nauseous  garlic-like  smell,  characteristic 
of  all  the  organic  sulphur  compounds. 

(~*    TT    ) 

Ethyl  Sulphide,   ~2  ,      >  S.     This  compound  in  the  sulphur 

series  is  analogous  to  £ther  in  the  oxygen  series  ;  it  is 
obtained  by  acting  on  potassium  sulphide,  K2  S,  with  ethyl 
chloride.  It  is  a  colorless  liquid,  boiling  at  91°,  and  posses 
sing  a  strong,  disagreeable  odor. 

C',,H'  1  o, 

Hydnc  Ethyl  Sulphate,    ~  Q  or  Sulphovinic  Acid,  is 

H2      O, 


260  Elementary  Chemistry. 

formed  when  alcohol  and  strong  sulphuric  acid  are  mixed.  It 
acts  as  an  acid,  and  forms  salts  in  which  the  typical  hydrogen 
is  replaced  by  a  metal.  The  ethyl  sulphates  of  the  alkalies 
and  alkaline  earths  are  soluble  salts,  and  crystallize  well. 

Di-Ethyl  Sulphate,  2J?a°H  5)  1  °'  is  obtained  bY  acting 
upon  ether  with  sulphuric  trioxide  ;  it  is  a  body  which  decom 
poses  on  distillation  and  on  addition  of  water. 

Ethyl  Phosphates  are  known  :  they  correspond  to  the  tri- 
basic  alkaline  phosphates  in  containing  either  i,  2,  or  3  mole 
cules  of  ethyl,  replacing  hydrogen  in  tribasic  phosphoric  acid. 
Thus  we  have  : 

Dihydric  Ethyl-  Hydric  Diethyl-  Triethyl- 

Phosphate.  Phosphate.  Phosphate. 

in  in  in 

PO      )  PO         )  PO         )  ~ 

C2  H6  [  03  2  (C,  H.)     [  03  3  (C,  HB)    ]  Oi 

Ha         )  H  ) 

II 

Ethyl  Carbonate,  2  (C  H  }   [  ^2,  corresponding  to  sodium 

n 
carbonate,  2/^a\  [•  Oa,  can  also  be  prepared. 

C   N  ) 

Ethyl  Cyanate,   ^   ^   V  O,  a  colorless   liquid,  boiling  at 

60°,  and  possessing  a  powerful  and  irritating  smell.  It  is 
formed  by  distilling  potassium-ethyl-sulphate  with  potassium 
cyanate.  In  contact  with  caustic  potash  it  forms  ethylamine, 
thus  : 


Ethyl  Borates  and  Silicates  likewise  exist. 

Ethyl,  or  Butyl-Hydride,  C<  Hio.  A  substance  having 
this  composition,  and  formerly  supposed  to  be  the  radical 
ethyl  in  the  free  state,  is  obtained  by  heating  to  150°  ethyl 
iodide  with  metallic  zinc  in  a  closed  tube.  From  this  body 


Elementary  Chemistry.  261 

no  ethyl  compounds  can  in  any  way  be  prepared  ;  but 
upon  treatment  with  chlorine  it  yields  the  chloride  of  the/0//? 
carbon  radical,  viz.,  C4  H9  Cl  butyl  chloride.  Hence  the  so- 
called  ethyl  must  be  looked  upon  as  butyl  hydride,C4H9H. 

C~*     T-T       } 

TRICARBON    SERIES.      Propyl   alcohol      '*         I  O,   has 


been  found  in  the  last  products  of  distillation  of  French 
brandies  ;  it  boils  at  96°,  dissolves  freely  in  water,  but  does 
not  mix  in  all  proportions.  Propyl  alcohol  unites  with 

c.  H,  i  0 

sulphuric  acid  to  form  hydric   propyl-sulphate,      £r\ 

H    f   ° 

The  propyl  compounds  have  not  been  much  studied  ;  they 
closely  resemble  the  foregoing  ethyl  series  of  bodies.  Propyl 
alcohol,  when  oxidized,  yields  propionic  acid  (see  p.  249). 

TETRA-CARBON  SERIES.     Butyl  alcohol,  C4     9  \  O.     Bu 


tyl  alcohol  is  found  in  the  oily  liquid  obtained  at  the  end  of 
the  distillation  of  spirits  from  the  beet-root  molasses.  It 
boils  at  109°,  and  resembles  common  alcohol  in  its  proper 
ties,  as  well  as  in  those  of  its  derivatives.  The  butyl,  ether, 
chloride,  iodide,  nitrate,  and  other  compounds,  are  known  ; 
they  are  prepared  in  the  same  manner  as  the  ethyl  compounds, 
and  possess  no  specially  note-worthy  properties. 

PENTA-CARBON  SERIES.    Amyl  alcohol,  Cs^11  I  O.  This 

alcohol  occurs  commonly  as  the  chief  constituent  of  the 
Fousel  oil  obtained  in  the  manufacture  of  potato  brandy, 
from  which  it  is  obtained  by  washing  with  water  and  subse 
quent  rectification.  It  is  a  colorless  liquid,  possessing  a  dis 
agreeable,  penetrating  smell  ;  it  dissolves  in  alcohol  and 
ether,  but  is  not  miscible  with  water.  Amyl  alcohol  boils  at 
132°,  and  solidifies  at  -  20°.  Amyl  alcohol,  like  the  fore 
going  alcohols,  forms,  with  sulphuric  acid,  hydric  amyl-sul- 


262  Elementary  Chemistry. 

phate,  which  yields  double  salts,  called  the  amyl  -sulphates  ;  it  is 
also  attacked  by  hydrochloric  acid,  amyl-chloride,  C6HUC1, 
being  formed.  Amyl  alcohol,  in  presence  of  oxygen  and  finely 
divided  platinum,  undergoes  oxidation  to  valeric  acid,  thus  : 

Amyl  Alcohol  Valeric  Acid. 


Potassium  and  sodium  can  replace  the  typical  hydrogen  of 
this  alcohol,  forming  potassium  or  sodium  amylate.  The 
iodide  and  bromide  are  prepared  in  the  same  way  as  the  cor 
responding  ethyl  compounds,  with  the  substitution  of  amyl- 
for  ethyl-alcohol. 

f    T-f      ) 
AmylEtktr,  C*H||  >  O,  is  a  colorless  liquid,  boiling  at 

176°,  obtained  by  the  action  of  amyl  iodide  upon  potassium 
or  sodium  amylate,  thus  :  — 

Amyl  Iodide    and          Sodium  •  Amyl  ,       Sodium 


T         j_ 

I 


•  y  , 

Amylate       glve  Ether  and  Iodide. 

s  HU   )   f^  CB  HH  )   -".  XT      T 

0     =  CB  HM  JO     +     Na  I. 


Amyl  Hydride,  C6H,i  H.  This  substance  is  a  volatile 
liquid,  boiling  at  30°,  obtained  by  heating  amyl  iodide  with 
zinc  and  water  ;  it  occurs,  together  with  all  the  hydrides  of 
this  series  of  alcohol  radicals,  in  American  petroleum,  and  in 
the  light  oils  from  th^  distillation  of  coal. 

The  mixed  methyl-amyl  and  ethyl-amyl  ethers,  have  already 
been  mentioned.  Amongst  the  compound  amyl  ethers,  the 

C*    T-T        ) 
acetate,  ^  ^!      V  O,  is  prepared  on  a  large  scale,  as  it  pos 


sesses  the  peculiar  odor  of  Jargonelle  pears,  and  it  is  used  in 
flavoring  cheap  confectionery.  This  compound  is  obtained 
by  distilling  amyl  alcohol  with  potassium  acetate  and  sulphuric 
acid  ;  it  can  also  be  prepared  by  heating  the  chloride  with 
potassium  acetate.  If  this  amyl  acetate  be  heated  with  potash, 
amyl-alcohol  and  potassium  acetate  are  formed. 


Elementary  Chemistry.  263 

Amyl          and        Potash    give      Amyl  and          Potassium 

Acetate  Alcohol  Acetate. 

i     +     K  1  Q    =     C5Hl1  \  O   +   Ca    Hs  ° 

H  j  H     )  K 

Amyl,  Cio  H22.  A  substance  having  this  composition  is 
obtained  by  acting  on  amyl  iodide  with  sodium.  It  is  a  color 
less  liquid,  boiling  at  158°,  from  which  none  of  the  amyl  com 
pounds  can  be  obtained,  but  which  yields  decatyl  chloride, 
CioH2i  Cl,  on  treatment  with  chlorine.  We,  therefore,  con 
sider  this  body  as  decatyl  hydride,  d0H2i  H,  and  as  not  be 
longing  to  the  amyl  group. 

HIGHER  ALCOHOLS.  The  alcohols  containing  6  to  10 
atoms  of  carbon  resemble  the  foregoing  series  in  their  general 
properties.  Hexyl  and  heptyl  alcohols  are  found  in  certain 
fermented  liquors ;  octyl  alcohol  is  obtained  by  distilling 
castor  oil  with  potash.  The  hydrides  of  these,  as  well  as  of 
all  the  higher  and  lower  alcohol  radicals,  are  found  in  American 
petroleum.  This  substance  consists  essentially  of  a  mixture 
of  these  various  hydrides  from  C  H4  (marsh  gas),  or  even  H2 
(hydrogen),  up  to  hydrides  which  are  solid,  and  contain  a 
very  large  number  of  atoms  of  carbon,  and  to  which  the  name 
of  Paraffine  has  been  given.  The  hydrides  can  be  separated 
from  each  other  by  repeated  rectifications,  and  obtained  in  the 
pure  state.  From  these  hydrides  the  corresponding  chlorides 
can  be  prepared  by  the  action  of  chlorine,  and  from  the 
chlorides  we  can  form  the  acetates  and  the  alcohols  them 
selves  (see  Amyl  Acetate). 

C   H     ) 
Cetyl  Alcohol,       16pj33  [•  O,  is  found  combined  with  palmitic 

acid  in  spermaceti.  It  forms  a  white  solid  crystalline  mass, 
but  acts  in  its  chemical  properties  like  an  alcohol :  thus  it 
forms  a  chloride,  CJ8  H3s  Cl,  also  a  bromide  and  iodide ;  it 

C     H     ) 

likewise  yields  an  ether,    ~16  „     [  O,  obtained  by  the  action 

Lie  H3s  \ 

of  cetyl  iodide  upon  potassium  cetylate  ;  and  a  compound  with 
Lie  Hss  ) 

sulphuric  acid,       SO3  >  O2.    Cetyl  alcohol  undergoes  oxida- 


Lje  Hss  ) 

ric  acid,       SOa  > 
H    ) 


264  Elementary  Chemistry. 

tion  when  heated  with  caustic  potash,  yielding  an  acid  in 
which  one  of  oxygen  replaces  two  of  hydrogen  of  the  alcohol, 
thus  : 

Cetyl  Alcohol        and        Potash        yield        Potassium         and  Hydrogen. 

Palmitate 

Cie  Has 

H 

This  palmitic  acid  bears  the  same  relation  to  cetyl  alcohol 
as  acetic  acid  does  to  common-  or  ethyl- alcohol. 

/—          TT  \ 

Cerotyl  Alcohol,  56  V  O,  is  contained  in  Chinese  wax  ; 

it  is  a  white  solid  solid,  crystalline  substance.  When  heated 
with  potash  it  undergoes  oxidation,  and  furnishes  an  acid, 

called  cerotic  acid,  C"  H53  °  j  O. 

Melisyl  Alcohol,  Cii0^61  i  O,  a  solid  white  substance  con 
tained  in  beeswax :  when  fused  with  potash  it  forms  an  acid 
termed  melissic  acid,Cso  59  °  O. 


LESSON   XXXI. 

COMPOUNDS  OF  THE  ALCOHOL  RADICALS  WITH  THE  NI 
TROGEN  (TRIAD)  GROUP  OF  ELEMENTS.  N.  P.  As. 
Sb.  Bi. 

I.    Compound  Alcoholic    Ammonias.      The    constitution 

C   H    ) 

of  the   primary  monamines,   as     '*  H*  V  N,  Ethylamine  ;  se- 

C2H6) 

condary  monamines,  as  C2  H6  >  N,   Dieth)-lamine  ;    and  ter- 
H   ) 


Elementary  Chemistry.  26$ 


tiary  monamines,  as  Triethylamine,  C2  H5  >•  N,  have   already 

C2  H5) 

been  mentioned  (p.  248).  These  bodies  are  volatile  ;  they  all 
have  a  strong  alkaline  reaction  and  ammoniacal  smell,  and 
they  combine  with  H  Cl,  &c.,  to  form  salts.  These  com 
pound  ammonias  are  formed  in  many  ways,  of  which  the 
most  important  are — 

1.  By  the  action  of  caustic  alkalies  on  the  cyanates  of  the 
alcohol  radicals  (see  p.  260). 

2.  By  the  action  of  the  iodides  of  these  radicals  on  am 
monia,  we  obtain  the  iodide  of  the  compound   ammonium, 
which,  when  treated  by  potash,  yields  the  compound  ammonia, 
thus, 

Ethyl  Iodide      and       Ammonia        give        Ethylamine  and        Hydriodic 

Acid. 

(C2H5)- 
C2H5" 


HI 

H>N        = 

H) 


Ethyl  iodide  acts  similarly  on  ethylamine,  giving  rise  to 
diethylamine  and  hydriotic  acid,  thus  : 

C2  H5 1  +  C2  H5,  H2  N  =  (C2  H5)2  H,  N  +  H  I, 

and  also  acts  upon  diethylamine  in  the  same  way,  giving  rise 
to  triethylamine,  thus  : 

C2  H3  I  +  (C2  H5)2  H  N  =  (C2  H5)3  N  +  H  I. 

Ethyl  iodide  also  combines  with  triethylamine  to  form  tetra- 
ethylammonium  iodide,  N  (C2H5)4 1.  In  practice  all  these 
compounds  are  formed  together  when  ethyl  iodide  acts  on 
ammonia.  The  compounds  of  mono-,  di-,  and  tri-ethylamine 
with  hydriodic  acid  are  decomposed  by  caustic  potash,  and 
the  volatile  compound  ammonias  liberated  ;  the  case  of  the 
tetra-ethyl-ammonium  iodide  is  different,  as  it  is  not  decom 
posed  by  potash,  but  yields,  when  treated  with  silver  hydroxide, 
a  hydrated  oxide,  which  is  non-volatile  without  decomposi- 

12 


266 


Elementary  Chemistry. 


tion,  and  is  analogous  in  constitution  and  similar  in  proper 
ties  to  caustic  potash. 


Tetra-ethylammonium 
Hydrate. 

(C,  H6)4  N 
H 


Potassium  Hydrate. 

K 
H 


By  acting  on  ethylamine  with  other  iodides,  such  as  methyl 
iodide,  mixed  amines  can  be  prepared.  The  compound  am 
monias  form  double  salts  with  platinic  chloride  ;  the  larger 
the  number  of  organic  radicals  contained,  the  more  soluble  is 
the  platinum  salt.  The  following  table  gives  the  names,  com 
positions,  and  boiling  points  of  the  most  important  of  the 
compound  ammonias.  It  will  be  seen  that  the  boiling  point 
increases  with  the  increasing  number  of  carbon  atoms,  con 
tained  in  the  compound. 


Primary  Monamines. 


CH3 

Methylamine     .....       H 

H 

C2H5 


Ethylamine     .     .     . 

H     J-N    . 

H     ) 
C3  H7  ) 

.   .  .       H  £N  . 

Butylamine    .     .     . 

H    ) 

C4H9  ) 

.     .     .          H     >N    . 

H    ) 

C5  Hn  ) 
.    .    .         H    >N    . 

H     \ 

Caproylamine,  or 

Hexylamine  ..... 


Cc  g13 
H 


XT 


Boiling  Point. 

below  o° 

i8°7 

49°. 


94° 
126° 


Elementary  Chemistry.  267 

Boiling  Point. 


Heptylamine H    V  N    .    .  146° 

H    ) 

C8  HIT  ) 

Octylamine VN    .    .  170° 

H    ) 


Secondary  Monamines. 

CH3  } 

Dimethylamine      ....      C  H3   >  N     .     .          80-5° 

H  ) 

CH3  ) 
Methyl-ethylamine     .    .    .     C3  H5  V  N    .    . 

C2H6  ) 

Diethylamine Ca  H5   >  N.    .  57  '5 

H    ) 

CB  H«  ) 

Diamylamine Ct  Hu  >  N    .    .  170° 

H    ) 

Tertiary  Monamines. 

CH3  ) 

Trimethylamine      ....     C  H3    >•  N    .    .        4° — 5° 

C  H3  ) 

CTT          \ 
a  his    1 

Triethylamine C2  H5   >  N     .     .  91° 

C2H6  ) 

C2H4  ) 

Diethyamylamine  .    .    .     .    C2  H5   >  N     .    .  154° 

Cs  Hn  ) 

C8  Hn  ) 

Triamylamine C5  Hn  >•  N     .    .  257° 

Cs  Hn  ) 


268  Elementary  Chemistry. 

Boiling  Point 

C   H3  ) 
Methyl-ethyl-amylamine     .     Ca  H6   >  N      ...     135° 


A  comparison  of  these  compounds  shows  that  it  is  possible 
to  have  two  or  more  bases  of  the  same  composition,  but  of 
different  constitution  ;  thus  C3H9N  stands  for  methyl-ethyla- 
mine  and  trimethylamine.  In  order  to  determine  the  consti 
tution  of  a  body  having  this  composition,  it  is  necessary  to 
ascertain  how  many  atoms  of  the  replaceable  hydrogen  of  the 
original  ammonia  it  contains. 

Phosphorus  bases.  Compounds  corresponding  to  the  pre 
ceding,  but  containing  phosphorus  instead  of  nitrogen,  have 


been  prepared  ;    thus,  triethyl-phosphine,    C2H5  >  P,   is    ob- 

C2H5  ) 

tained  by  acting  upon  zinc  ethyl  with  phosphoric  trichloride, 
the  chlorine  changing  places  with  ethyl. 

Triethylphosphine  is  a  colorless  liquid,  boiling  at  I27°'5, 
possessing  a  powerful  and  disagreeable  smell.  It  combines 
directly  with  oxygen,  sulphur,  and  chlorine,  in  this  respect 
differing  from  the  foregoing  nitrogen  bases.  With  ethyl 
iodide  it  combines  and  forms  iodide  of  tetra-ethyl  phospho- 
nium,  P(C2H5)J,  from  which  a  strongly  caustic  hydrate, 
analogous  to  the  corresponding  nitrogen  compound,  can  be 
obtained  by  the  action  of  silver  oxide  (p.  265). 

Arsenic  bases.  The  compounds  of  arsenic  with  the  alcohol 
radicals  differ  somewhat  in  constitution  from  the  foregoing, 
inasmuch  as  we  are  acquainted  in  the  methyl  series  with  (i) 
tri-methyl-arsine  (CH3)3As  ;  (2)  arsendimethyl  (CH3)2As  ; 
(3)  arsen-monomethyl  (CH3)As.  The  first  of  these  is  con 
structed  on  the  type  ammonia,  and  the  two  latter  combine 
directly  with  one  and  two  atoms  of  chlorine  respectively,  and 
then  form  compounds  belonging  to  the  general  type,  NH3. 
We  thus  have  the  following  compounds  known  : 

As     H      H       H    Arseniuretted  hydrogen. 

As  CH3  CH8  CH3  Trimethyl-arsine. 


Elementary  Chemistry.  269 

As  CH3  CH3     Cl    Arsendimethyl  chloride. 

As  CH3     Cl      Cl    Arsenmonomethyl  dichloride. 

As     Cl      Cl      Cl    Arsenic  trichloride. 

Trimethylarsine  is  a  colorless  liquid,  boiling  at  120°,  formed 
by  the  action  of  methyl-iodide  on  an  alloy  of  sodium  and 
arsenic ;  it  corresponds  to  trimethylamine  and  trimethyl 
phosphine. 

Arsendimethyl,  or  CacodyL  This  substance  is  prepared  by 
heating  arsenious  oxide  with  potassium  acetate.  Cacodyl  is 
a  colorless  liquid,  boiling  at  170°,  which  takes  fire  in  contact 
with  the  air.  It  is  extremely  poisonous,  and  possesses  a 
most  disagreeable  garlic-like  smell,  and  must  be  prepared 
with  great  care.  It  combines  with  chlorine,  oxygen,  &c., 
and  plays  the  part  of  an  organo-metallic  radical.  One  of  the 

most  important  compounds  is  cacodylic  acid,      '  ^   TT       f  Oa ; 

it  is  soluble  in  water,  and  is  not  poisonous.  The  formation 
of  cacodyl  and  its  oxide  in  the  mode  Described,  may  be  used 
as  a  delicate  test  for  the  presence  of  arsenic,  from  the  strong 
and  characteristic  odor  of  this  body. 

Antimony  bases.  By  acting  on  ethyl  iodide  with  an  alloy 
of  antimony  and  potassium,  a  compound  called  tri-ethyl 


stibine,  C2H5  J-  Sb,   has    been    prepared ;    it   is   a  colorless 

C2H5 

liquid,  boiling  at  I58°'5,  which  takes  fire  and  burns  in  con 
tact  with  the  air.  It  forms  compounds  with  oxygen,  sulphur, 
and  chlorine. 

Bismuth    forms   an  analogous    compound,    Triethbismu- 

C2H6) 
tine,  C2H5  >  Bi.     Boron  also  unites  with  three  molecules  of 

C2H6) 

ethyl  to  form  a  colorless  liquid,  which  takes  fire  when  brought 
in  contact  with  air,  and  burns  with  a  green^flante..^  . 

J  '    />    f /     i 


"•«  r  (  i/^vr 


270  Elementary  Chemistry. 

Compounds  of  the  Alcohol  Radicals  with  Metals. 

C  H  ) 

Zinc  Ethyl,  £  ji*  [  Zn.  This  important  substance  is  ob 
tained  by  the  action  of  zinc  upon  ethyl  iodide  ;  it  is  a  colorless 
liquid,  boiling  at  118°  ;  it  takes  fire  and  burns  with  a  green 
ish  flame  in  contact  with  air  or  oxygen,  and  forms  zinc 

C-  H    ) 
ethylate,    ^n  °  [  °'  when  the  oxidation  goes  on  slowly.    Zinc 

Ethyl  is  a  valuable  reagent,  by  means  of  which  many  other 
compounds  can  be  obtained  :  thus,  if  we  act  with  this  sub 
stance  on  silicic  chloride,  we  get  zinc  chloride  and  silicon 
ethyl;  on  mercuric  chloride,  we  obtain  mercuric  ethyl  j  on 
lead  chloride,  we  get  lead  ethyl.  Zinc  methyl  and  zinc  amy] 
are  also  known.  Compounds  of  tin,  lead,  and  a  few  other 
metals  with  the  alcohol  radicals,  can  be  prepared,  possessing 
properties  somewhat  analogous  to  the  foregoing  substances. 

Compounds  of  the  alkaline  metals  with  ethyl  have  been 
obtained  by  acting  upon  these  metals  with  zinc  ethyl.  Sodium 
Ethyl  combines  directly  with  carbonic  dioxide,  and  forms 
sodium  propionate  (p.  249),  thus : 

Sodium  Ethyl  and  Carbonic  Dioxide    yield    Sodium  Propionate. 

Na(C3H6)  +  CO2        =         C3H5NaO2. 


LESSON  XXXII. 
COMPOUNDS  DERIVED  BY  OXIDATION  FROM  THE  ALCOHOLS. 

Group  of  Fatty  Acids  and  their  derivatives.  The  mode 
in  which  the  aldehydes  and  acids  are  connected  with  the  cor 
responding  alcohols  has  been  already  described  (p.  247). 
These  oxidized  products  contain  a  radical  in  which  one  atom 
of  oxygen  is  substituted  for  two  of  hydrogen  in  the  alcohol 
radical. 


Elementary  Chemistry.  271 

H  ) 
Thus  we  have  on  the  type  jj  Mn  the  di-carbon  series  — 

Aldehyde.  Acetone.  Acetyl  Chloride. 

C2H3O  )  C2H30  )  C2H3O  \ 

H  f  CH3  \  d  j 

TT    \ 

and  on  the  water  type,  ^  j-  O 


Hydric  Acetate.    Potassium  Acetate.     Ethyl  Acetate.         Acetyl  Acetate. 

C2H30  )  0          C2H30  )  0      C2H30  \  0       C2H30  }  o 
Hf°  Kf  C      C2    H6f°        C2H3Of°* 

If  the  typical  oxygen  of  the  water  be  replaced  by  sulphur, 
we  get  — 

Hydric  Thiacetate.         Potassium  Thiacetate.          Ethyl  Thiacetate. 

C3H3O  \  c  C2H3O|Q  C2H30 

Hjb  Kfb  C2H5 

Of  the  ammonia  type  we  have  the  amides  :  thus  — 

C2H30  ) 

Acetamide  H     \  N. 

H    ) 

The  following  are  the  most  important  reactions,  by  means 
of  which  the  monobasic  acids  can  be  obtained  : 

1.  From  the  alcohol  having  the  same  number  of  carbon 
atoms  by  direct  oxidation. 

2.  From  the  alcohol  containing  one  atom  less  carbon,  as 
follows  : 

(a)  By  decomposition  of  the  alcoholic  cyanide  by  potash, 
ethyl  cyanide  yielding  propionic  acid  (see  p.  258). 

(b}  By  acting  with  the  sodium  compound  on  carbonic  acid  ; 
sodium  ethyl  and  carbonic  acid  yielding  sodium  propionate 
(see  p.  270). 

MONOCARBON    SERIES.     Formic  Arid,      H    I  O.       This 

acid  occurs  ready  formed  in  the  bodies  of  red  ants,  whence 
its  name  ;  it  is  likewise  found  in  stinging-nettles.     Formic 


272  Elementary  Chemistry. 

acid  is  obtained  by  the  oxidation  of  methyl  alcohol,  as  well  as 
of  sugar,  starch,  and  other  organic  bodies.  It  is  formed 
synthetically  by  acting  upon  potash  with  carbonic  oxide  gas 
at  100°,  thus  : 

Carbonic  Oxide  and  Potash    yield    Potassium  Formate. 

ro  H  )  0  CHO  )  0 

K|°  K    f° 

Formic  acid,  diluted  with  water,  can  be  best  prepared  by 
decomposing  oxalic  acid,  in  presence  of  glycerine  and  water, 
into  formic  acid  and  carbonic  dioxide,  thus  : 

Oxalic  Acid  yields  Formic  Acid  and  Carbonic  Dioxide. 
C2H2O4       =       CHaOa       +       C02. 

In  order  to  obtain  formic  acid  in  the  pure  glacial  state,  free 
from  water,  the  lead  formate  is  decomposed  by  a  current  of 
sulphuretted  hydrogen  gas,  and  lead  sulphide  and  formic 
acid  are  produced.  Formic  acid  is  a  colorless  liquid,  possess 
ing  a  peculiar  sharp  smell  and  strong  acid  taste.  It  boils  at 
100°,  and  below  i°  it  solidifies  to  a  white  crystalline  mass; 
its  specific  gravity  at  o°  is  1-235,  and  it  is  miscible  in  all  pro 
portions  with  water.  Heated  with  sulphuric  acid,  it  forms 
water  and  pure  carbonic  oxide  gas,  and  oxidizing  agents  con 
vert  it  easily  into  carbonic  acid  and  water.  A  formate, 
heated  with  excess  of  baryta,  yields  oxalate,  thus  : 

Formic  Acid    yields    Oxalic  Acid  and  Hydrogen. 

2(CH2O2)     =     CaHaO4     +     Ha. 

Formic  acid  is  monobasic  ;  and  forms  well-crystallizable 
salts  called  Formates  :  all  the  formates  are  soluble  in  water. 
It  may  be  distinguished  by  its  power  of  reducing  metallic 
mercury  and  silver,  as  a  gray  powder,  from  the  nitrates  on 
boiling. 

CHO) 

Formamide,      H      V  N.       Obtained    by  acting  on   ethyl 


formate  with   ammonia.     It  is  a  colorless  liquid,  boiling  at 
194°.     The  aldehyde  of  the  monocarbon  series  is  not  known. 


Elementary  Chemistry.  273 

DICARBON  SERIES. — Acetyl  Compounds. 

Aldehyde,  Ca  H^°  | .  Acetyl  hydride  is  obtained  by  oxidi 
zing  dilute  alcohol  by  means  of  a  mixture  of  manganese  diox 
ide  and  sulphuric  acid.  It  may  also  be  prepared  by  distil 
ling  a  mixture  of  an  alkaline  acetate  and  formate,  thus  : 

Potassium  Acetate  and  Formate.  Aldehyde.     Potassium  Carbonate. 

C2H3KO2  +  CHK08  =  C2H4O  +  K2  C  O2. 

It  is  a  colorless,  suffocating-smelling  liquid,  boiling  at  21° ; 
it  has  a  specific  gravity  of  0*801  at  o°,  and  mixes  in  all  pro 
portions  with  water,  alcohol,  and  ether.  Aldehyde  reduces 
metallic  silver,  depositing  it  as  a  bright  mirror  from  solutions 
of  the  nitrate,  and  this  reaction  may  be  used  to  detect  the 
presence  of  the  substance.  It  unites  directly  with  nascent 
hydrogen  to  form  alcohol,  C2H4  O  +  H2  =  C2  H6  O  ;  it  like 
wise  forms  acetyl  chloride  when  treated  with  chlorine,  and 
acetic  acid  when  acted  upon  by  oxidizing  agents.  Aldehyde 
is  capable  of  existing  in  three  other  peculiar  states,  or  of  un 
dergoing  polymeric  modifications.  If  it  is  preserved  in  con 
tact  with  excess  of  acid  it  remains  unchanged,  but  if  it  be 
pure  it  soon  deposits  a  solid  substance  having  the  same  com 
position  as  aldehyde,  and  termed  Metaldehyde ;  this  sub 
stance  sublimes  unchanged  at  120°,  but,  when  heated  to  200° 
in  a  closed  tube,  it  forms  aldehyde  again.  Paraldehyde  is  an 
other  modification,  and  is  a  liquid  boiling  at  124°  ;  and  a 
third  modification  termed  Acraldthyde,  boils  at  110°.  The 
molecular  formula  of  paraldehyde  appears  to  be,  C6  HJ2  O3, 
or  3  (Ca  H4  O)  ;  that  of  acraldehyde,  C4  H8  O2,  or  2  (C2  H4  O). 
Aldehyde  is  also  isomeric  with  ethylene  oxide  (p.  283). 
Aldehyde  forms  a  crystalline  compound  with  ammonia, 

termed  Aldehyde-ammonia,     2  ^  3^    !• ,  and  it  also  unites  with 

hydric  sodium    sulphite    to    form  a  solid   compound.      In 
many  reactions  aldehyde  comports  itself  as  the  oxide  of  a 

dyad,  (Ct'iiO  O. 

12* 


274  Elementary  Chemistry. 

ii 

f    T-T       •") 

Acetal.  fc?  TT\   \  O2.     This  substance  is  a  derivative  of 
(C3  Hs)2  j 

ii 

aldehyde,  in  which  this  dyad  radical  aldehydene,  C2  H4, 
occurs.  It  is  obtained  by  heating  aldehyde  and  alcohol 
together,  and  is  formed  together  with  aldehyde  when  al 
cohol  is  oxidized  with  sulphuric  acid  and  manganese  di 
oxide.  A  compound  of  a  similar  constitution,  viz.,  dime- 

ii 

f*    T-T    ) 
thy  I  acetal,  ,^  "^  .4  C  O2,  occurs  in  crude  wood  spirit.     Acetal 

is  isomeric  with  diethyl  glycol  (see  p.  284). 

Chloral,     2  ^       t  This  substance  may  be  considered  as 

aldehyde,  in  which  3  of  chlorine  take  the  place  of  3  of  hydro 
gen  ;  and  although  it  has  not  been  directly  prepared  from 
aldehyde,  yet  it  resembles  it  in  many  properties,  such  as 
forming  a  crystalline  compound  with  ammonia,  which  reduces 
silver  salts.  Chloral  is  obtained  by  the  continued  action  of 
chlorine  upon  alcohol ;  it  is  a  colorless  powerfully-smelling 
liquid,  boiling  at  99°. 

Acetic  Acid,  C2  j^3  °  i  O.     Dilute  acetic  acid  has  been 

known  as  vinegar  from  very  early  times  ;  it  occurs  in  the 
juices  of  certain  plants  and  vegetables,  but  only  in  small 
quantities.  The  most  important  modes  of  preparing  acetic 
acid  are:  (i)  the  method  generally  practically  employed  by 
the  oxidation  of  alcohol ;  (2)  the  theoretically  interesting  pro 
cesses,  ist, — the  direct  combination  of  carbonic  acid  and 
sodium  methyl,  thus : 

C  H3  Na  +  CO2  =  C2  H3  O 
Na 

and  2d,  by  the  action  of  potash  on  methyl  cyanide,  thus : 


Elementary  Chemistry.  275 

(3)  Acetic  acid  is  also  prepared  on  a  large  scale  by  the  dry 
distillation  of  wood ;  the  crude  acid  thus  obtained  is  com 
monly  called  Pyroligneous  Acid. 

Pure  acetic  acid  is  obtained  by  decomposing  the  acetates. 
The  process  by  which  alcoholic  liquids  (beer  or  wine)  yield 
acetic  acid  by  oxidation  is  termed  the  Acetous  Fermentation 
(see  p.  313):  the  liquids  are  exposed  to  the  air  at  a  tempera 
ture  of  about  25°,  for  a  fortnight,  when  the  alcohol  is  changed 
to  vinegar.  This  change  appears  to  be  brought  about  by  the 
presence  of  a  peculiar  vegetable  growth  (tnycoderma  aceti) 
which  floats  on  the  surface  of  the  liquid,  first  absorbing  the 
oxygen,  and  then  giving  it  up  to  the  alcohol. 

Acetic  acid  in  the  pure  state  is  obtained  by  heating  sodium 
acetate  with  strong  sulphuric  acid :  it  is  a  colorless  liquid, 
boiling  at  118°  and  solidifying  to  an  ice-like  mass  at  17°,  and 
hence  the  name  of  Glacial  Acetic  Acid  has  been  given  to  it. 
It  possesses  a  peculiar  sharp  smell,  and  has  a  strong  acid 
taste  ;  it  mixes  in  all  proportions  with  water,  but  when  dis 
tilled  the  mixture  has  no  definite  boiling  point ;  the  residue 
becomes  stronger  until  glacial  acid  remains.  Acetic  acid  may 
be  recognized  by  its  smell,  and  by  the  formation  of  ethyl 
acetate ;  also  by  the  production  of  cacodyl  when  an  acetate  is 
heated  with  arsenious  oxide.  Acetic  acid  is  monobasic,  and 
forms  a  series  of  well-defined  salts  termed  Acetates.  The 
acetates  of  the  alkalies  are  soluble  crystallizable  salts. 
Aluminium  and  ferric  acetates  are  soluble  compounds  used  in 
large  quantities  as  mordants  by  dyers  and  calico-printers 
under  the  commercial  names  of  Red  Liquor  and  Iron  Liquor. 
Lead  acetate,  or  sugar  of  lead,  and  copper  acetate,  or  verdigris, 
are  the  most  important  compounds  of  acetic  acid  and  the  heavy 
metals.  The  radicals  methyl  and  ethyl,  &c.,  can  be  substi 
tuted  for  the  atom  of  typical  hydrogen  in  acetic  acid  forming 
the  compound  ethers  (see  ante,  page  247). 

Acetyl  Chloride,  C2H3OC1,  is  obtained  by  the  action  of 
phosphoric  oxychloride  upon  sodium  acetate.  It  is  a  color 
less  liquid,  fuming  strongly  in  the  air,  and  boiling  at  55°. 
The  corresponding  bromide  and  iodide  are  known. 


276  Elementary  Chemistry 

Acetyl  Acetate,  §.  g*.  Q  |  °>  or  Acetic  Anhydride,  is  a 


colorless  liquid,  boiling  at  138°,  formed  by  the  action  of  acetyl 
chloride,  or  phosphoric  oxychloride  upon  sodium  acetate, 
thus  : 

AC  H  n  Na  4-  pnn    -  <?/Ca  H3  °  I  n  ^1  +  3NaCl 
C13-2VC2H30{°;  +  POaNa. 

It  is  decomposed  by  boiling  with  water  into  two  molecules 
of  acetic  acid. 

Chloracetic  Acids.  Chlorine  acts  upon  acetic  acid  in  re 
placing  one,  two,  or  three  atoms  of  the  hydrogen  of  the  radi 
cal  acetyl  by  chlorine  :  we  thus  obtain  monochloracetic 

acid,  Ca  H'  £  °  j  O  ;  dichloracetic  acid?*  H  Cla  °  |  O  ;  and 
trichloracetic  acid,  Ca  3  I  O.  These  three  bodies  are 


crystalline  solids  :  the  first  fuses  at  62°,  and  boils  about  186°, 
the  second  boils  at  195° ;  and  the  third  boils  about  200°.  They 
form  salts  analogous  to  the  acetate  ;  and  acetic  acid  may  be 
regenerated  from  them  by  the  action  of  nascent  hydrogen. 

Thiacetic  Acid,  Ca  Hs         S.      This   substance   stands   to 


acetic  acid  in  the  same  relation  as  mercaptan  to  alcohol 
(p.  259)  ;  it  is  prepared  by  the  action  of  pentasulphide  of 
phosphorus  on  acetic  acid. 

P2  S5  +  5  C2  H4  O2  =  P2  O6  +  5  C2  H4  O  S. 
It  is  a  colorless  liquid,  possessing  a  peculiarly  nauseous 

smell,  and  boiling  at  93°.  The  anhydride,  £|  jj«  O  j  S'  is 
also  known. 

Acetyl  Peroxide,  ^  j          t  O2,  is  a  remarkable  compound, 

obtained  by  the  action  of  barium  dioxide  upon  acetic  acetate. 
It  is  a  thick  liquid,  possessing  energetic  oxidizing  properties, 
and  on  heating  it  decomposes  with  explosive  violence. 


Elementary  Chemistry.  277 

d  H3  O  ) 

Acetamide,       H        >  N,  is  the  acetyl  ammonia  ;  it  is  ob- 

H        J 

tained  by  the  action  of  ammonia  upon  ethyl  acetate  by  an 
exchange  of  acetyl  for  hydrogen,  thus  : 

H  )  C2  H3  O 

I    TVT       i         r 

:2H6 

It  is  also  formed  by  the  action  of  ammonia  on  acetyl 
chloride,  and  by  the  dry  distillation  of  ammonium  acetate. 
Acetamide  is  a  colorless  solid,  fusing  at  78°,  and  boiling  at 

222°. 

C2H30 
Diacetamide,   C2  H3  O  J-  N,        and       Ethyl-Diacetamide, 


C2  H3  O  ) 

C2  H3  O  >  N,    are  also  known.     Corresponding  compounds 

C2H5       ) 

are  likewise  formed  from  the  chloracetic  acids. 

Acetone,  p2  j          I  .     This  compound,  which   may  be  re 

garded  as  methyl  acetyl,  is  formed  by  replacing  the  chlorine 
in  acetyl  chloride  by  methyl,  thus  : 


C2H8O)\          /C2  H3  O 


/C2H8O)\       „  / 
(  Cl|  )=2( 


rl 


It  is  also  obtained  by  the  distillation  of  calcium  acetate,  or 
by  passing  the  vapor  of  acetic  acid  through  a  red-hot  tube. 
Acetone  is  a  colorless  liquid,  boiling  at  56°,  forming,  like 
aldehyde,  a  crystallizable  compound  with  hydric  sodium  sul 
phite.  By  the  action  of  sodium  amalgam  on  a  mixture  of 
water  and  acetone,  2  atoms  of  hydrogen  are  taken  up,  and  a 
substance  formed  which  is  isomeric  with  propylic  alcohol, 
thus  (p.  261)  : 

C3  H6  O  +  Ha  =  C3  H8  O. 

Acetylene,  C2  H2.  This  remarkable  substance  is  obtained 
by  the  direct  combination  of  carbon  and  hydrogen  at  a  very 


278  Elementary  Chemistry. 

high  temperature.  For  this  purpose  the  carbon  terminals  of 
a  powerful  battery  are  brought  together  in  an  atmosphere  of 
hydrogen  ;  acetylene  is  formed  and  precipitated  in  combina 
tion  with  copper  as  a  red  powder,  when  the  gas  is  passed 
through  a  solution  of  ammoniacal  cuprous  chloride.  Acety 
lene  is  formed  in  all  cases  of  incomplete  combustion  of  car 
bon  compounds,  also  when  the  vapor  of  alcohol  is  passed 
through  a  red-hot  tube,  and  it  is  contained  in  small  quanti 
ties  in  coal  gas.  It  is  a  colorless  gas,  possessing  a  peculiar 
and  unpleasant  odor  ;  it  burns  with  a  luminous  smoky  flame, 
and  combines  directly  with  chlorine  and  bromine. 

HIGHER  FATTY  ACIDS.  The  names,  composition,  and 
boiling  points  of  these  acids  have  already  been  given  (p.  249). 
In  their  general  characteristics  they  closely  resemble  the  first 
two  of  the  series,  formic  and  acetic  acid.  They  occur  in 
many  natural  fats,  and  they  are  all  formed  by  the  action  of 
nitric  acid  upon  mutton  or  beef  stearine  (p.  305). 

These  acids  may  be  prepared  synthetically  by  the  following 
important  reactions  :  (i)  by  the  direct  combination  of  car 
bonic  acid  with  the  sodium  compound  of  the  next  lower  alcohol 
radical  (p.  274)  ;  (2)  by  the  action  of  potash  on  the  cyanide 
of  the  next  lower  alcohol  radical  (p.  258)  ;  and  (3)  by  replac 
ing  i  or  2  atoms  of  hydrogen  in  the  radicals  of  the  fatty  acids 
by  alcohol  radicals.  They  are  most  of  them  oily  liquids 
slightly  soluble  in  water,  easily  soluble  in  alcohol,  and  each 
forms  a  well-defined  series  of  salts.  The  higher  members  of 
the  series,  especially  palmitic  and  stearic,  occur  in  all  fatty 
bodies ;  they  are  solid  substances  obtained  by  decomposing 
soaps  made  from  palm-oil  or  beef-suet,  which  consist  of 
sodium  or  potassium  palmitate  and  stearate  (see  Fats,  p.  305). 
These  acids  form  anhydrides,  compound  ethers,  chlorides, 
aldehydes,  amides  and  acetones,  corresponding  in  constitu 
tion  and  in  general  chemical  characters  with  the  same  com 
pounds  in  the  acetyl  series.  For  the  description  of  the 
properties  of  these  compounds  a  larger  work  on  Organic 
Chemistry  must  be  consulted. 

The  general  reactions  of  the  group  of  monatomic  alcohols 


Elementary  Chemistry.  279 

and  acids  which  offer  the  greatest  theoretical  interest  are, 
certainly,  those  by  which  it  is  possible,  in  the  first  place,  to 
prepare  the  most  simple  terms  of  the  series  synthetically  from 
their  elements,  and,  secondly,  to  pass  directly  by  addition  of 
carbon  and  hydrogen  from  these  lower  terms  to  the  higher 
ones,  and  thus  to  mount  up  the  series.  Suppose  that  we 
begin  with  methyl  alcohol  obtained  from  inorganic  sources  ; 
viz. :  (i)  Marsh  gas  prepared  from  sulphuretted  hydrogen  and 
carbonic  disulphide,  thus  : 

2  SH2  +  CS2  +  Cu8  =  CH4  -1-  4  (Cu2  S). 

(2)  Methyl  chloride,  from  this  by  the  action  of  chlorine,  thus : 

CH4  +  Cla  =  CH3  Cl  +  HCL 

(3)  Methyl  alcohol,  from  this  by  the  action  of  potash,  thus  : 

CH3  Cl  +  KHO  =  CH4  O  +  K  Cl. 

There  are  now  several  modes  by  which  we  can  pass  to  the 
dicarbon  series  : — 

(i.)  From  methyl  alcohol  we  prepare  methyl  cyanide  ;  this, 
on  decomposition  with  potash,  yields  acetic  acid  (see  p.  275), 
thus  : 

CNCHs  +  KHO  +  HaO  =  C3  H3  KO2  +  NH3 ; 

we  cannot  directly  reduce  the  acids  to  alcohols,  but  we  can  1 
obtain  aldehyde  from  acetic  acid  by  distilling  it  with  a  formate  I 
(p.  273),  thus : 

C2  H3KO3  +  CHKO2  =  C2H4  O  +K2  CO3 ; 

and  from  aldehyde  we  can  obtain  ethyl  alcohol  directly  by  the 
action  of  hydrogen  (p.  273),  thus  : 

C2  H4  O  +  H2  =  C2  H6  O. 

(2.)  From  methyl  alcohol  we  prepare  methyl  cyanide,  and 
by  acting  upon  this  with  hydrogen,  we  get  ethylamine  (p. 
252),  thus : 


280  Elementary  Chemistry. 

CNCH< 


Ethylamine  acted  upon  by  nitric  trioxide  yields  ethyl  nitrite, 
which,  on  decomposition  with  potash,  yields  the  alcohol,  thus  : 

C3  H7  N  +  Na  O3  =  C2  H5  NO2  +  H2  O  +  Na 
and        C2  H8  NO2  +  KHO  =  C2  H6  O  +  K  NO2. 

(3.)  From  methyl  alcohol,  by  the  action  of  zinc  on  methyl 
iodide,  we  prepare  the  so-called  radical  methyl:  this  sub 
stance  forms  ethyl  chloride  when  treated  with  chlorine  ;  from 
this  we  can  pass  through  ethyl  acetate  to  ethyl  alcohol.  The 
repetition  of  any  of  these  three  processes  would  enable  us  to 
pass  to  the  tricarbon  group,  and  so  on. 


LESSON  XXXIII. 

DIATOMIC  ALCOHOLS  AND  THEIR  DERIVATIVES. 

As  we  have  seen  (p.  229),  the  hydrocarbons  of  the  general 
formula,  Cn  H2n,  of  which  we  may  take  ethylene,  C2  H4,  as  an 
example,  are  non-saturated  compounds,  in  which  two  of  the 
combining  powers  of  the  carbon  are  not  satisfied  ;  hence  these 
bodies  combine  directly  with  two  atoms  of  chlorine,  bromine, 
&c.,  to  form  a  saturated  compound.  The  lowest  term  of  the 
series,  CH2,  to  which  the  name  of  methylene  has  been  given, 
is  not  known  in  the  free  state,  although  its  iodide,  C  H2  I2, 
has  been  isolated.  The  corresponding  diatomic  alcohol  also 
has  not  been  prepared,  but  the  diacetate  is  known. 

Ethylene,  C2  H4.  This  substance,  known  as  olefiant  gas, 
has  already  been  mentioned  (p.  78)  ;  it  is  formed  in  the  dry 
distillation  of  coal  and  various  organic  bodies  ;  it  is,  however, 
best  prepared  by  the  action  of  hot  sulphuric  acid  on  alcohol ; 
a  mixture  of  I  part  of  alcohol  and  4  parts  of  sulphuric  acid  is 


Elementary  Chemistry.  281 

heated  in  a  flask  with  enough  sand  to  form  a  pasty  mass. 
The  decomposition  is  a  very  simple  one  ;  alcohol  loses  I 
molecule  of  water,  H^O,  and  ethylene  is  formed.  The  chief 
physical  properties  of  ethylene  have  already  been  mentioned 
(p.  79).  It  combines  directly  with  2  atoms  of  chlorine,  also 
with  hydrochloric  and  hydriodic  acids  ;  with  chlorine  it  forms 
ethylene  dichloride  ;  with  the  hydracids  it  forms  ethyl 
chloride,  bromide,  or  iodide. 
ii 

Ethylene  dichloride,  C2  H4  C12.  Olefiant  gas  derives  this 
name  from  its  power  of  forming  an  oil  when  brought  into  con 
tact  with  chlorine.  On  mixing  these  gases,  drops  are  formed  ; 
and  when  collected,  washed,  and  distilled,  they  yield  the  pure 
dichloride,  This  body  boils  at  820-5,  and  is  insoluble  in 
water,  but  soluble  in  alcohol  and  ether.  It  is  rapidly  attacked 
by  chlorine,  and  substitution  products  are  formed,  in  which 
one,  two,  three,  and  lastly,  four  atoms  of  hydrogen  are  re 
placed  by  chlorine.  Thus  we  have  — 

Boiling  Point. 
C2  H4  Cla  82°'5 

C2H3C1C12  115° 

C2  H2  Cla  Cla  137° 

C2  H  Cl,  Cla  154° 

C2  Cla  I82° 

From  ethyl  chloride  a  series  of  chlorine  substitution  pro 
ducts  are  obtained,  identical  in  composition,  but  differing  in 
their  properties  from  the  foregoing  ;  thus,  the  two  sets  of 
bodies  boil  at  different  temperatures  ;  whilst  those  from 
ethylene  are  decomposed  by  alcoholic  potash,  those  from  ethyl 
chloride  remain  unchanged.  Th'ese  two  series  of  bodies  are 
said  to  be  isomeric.  The  last  term,  C2  C18,  is  identical  in  both 
series. 


Gfycolat  Ethylene  Alcohol^  C2  H4  >  O2.     This     substance, 

H, 

which  may  be  supposed  to  be  2  molecules  of  water,  in  which 
2  atoms  of  the  hydrogen  are  replaced  by  the  dyad  radical 


282  Elementary  Chemistry. 

ethylene,  is  obtained  by  the  action  of  ethylene  dibromide  upon 
silver  acetate,  silver  bromide  and  glycol  diacetate  being 
formed,  thus  : 

Ethylene    Di-bromide  and   Silver   Acetate  yield  Silver   and  Glycol  Diacetate. 

Bromide 

C2  H3  O 

C3  H4  Br2  +  2(C2A^3°  |  O  )  =  2  Ag  Br  +  Ca 


The  pure  glycol  is  obtained  from  the  acetate  by  acting  on 
it  with  baryta.  Glycol  is  a  colorless,  inodorous,  and  sweet 
ish-tasting,  thick  liquid;  its  specific  gravity  at  o°  is  I'I25,  it 
boils  at  I97°'5,  and  it  is  soluble  in  all  proportions  in  alcohol 
and  water.  When  exposed  to  air  in  contact  with  water  and 
platinum  black,  it  absorbs  oxygen  rapidly,  and  is  converted 
into  glycolic  acid,  thus  : 

C2  H6  O3  +  O2  =  H3  O  +  Ca  H4  O3. 

Glycol,  when  heated  to  240°,  with  caustic  potash,  gives  off 
hydrogen  and  forms  potassium  oxalate, 

C2  He  O2  4-  2  K  H  O  =  C2  K2  O4  +  8  H. 

From  these  reactions  it  would  appear  that  glycolic  and 
oxalic  acids  stand  to  glycol  as  acetic  acid  does  to  ethyl  alco 
hol.  Glycol  likewise  forms  an  aldehyde  by  loss  of  H4,  the 
substance  having  the  composition  C2  H2  O2,  and  called 
Glyoxal.  Glycol  acts  like  alcohol  in  other  respects  ;  the 
typical  hydrogen  can  be  replaced  by  sodium,  forming  com 
pounds  analogous  to  sodium  ethylate  ;  it  also  forms  a  com 
pound  with  sulphuric  acid,  called  glycol-sulphuric  acid, 

ii 
C2H4 

O3  ;  and  when  heated  with  hydriodic  acid,  it  forms 
SO2 
H3 
ethylene  iodide  and  water. 


Elementary  Chemistry.  283 

Glycol  differs,  however,  from  alcohol,  inasmuch  as  it  forms 
two  acids,  two  chlorides,  &c.  Thus  by  the  action  of  hydro 
chloric  acid  on  glycol,  the  first  product  obtained  is  glycol 
chlorhydrine,  that  is,  glycol  in  which  i  atom  of  Cl  takes  the 
place  of  the  monad  group,  HO  ;  whilst  by  the  further  action 
of  chlorine  a  second  replacement  of  the  same  kind  occurs, 
and  ethylene  chloride  is  formed. 

(i)  Glycol.  (2)  Glycol  Chlorhydrine.  (3)  Ethylene  Chloride. 

n    )  H      >0 

Ca  H4  >  Oa  n      r  n  r*   w   r~\ 

TT  \  C       H    "1 

The  first  of  these  bodies  is  built  on  the  type  of  2  molecules 
of  water,  the  second  on  a  mixed  type  of  i  of  water  and  i  of 
hydrochloric  acid,  and  the  third  on  the  type  of  2  of  hydro 
chloric  acid.  There  are  also  2  acetates  of  glycol  known, 
monoacetate  and  diacetate  ;  two  ethyl  compounds,  mono- 
ethyl  glycol  and  di-ethyl  glycol :  this  latter  body  is  isomeric 
with  acetal  (p.  274). 

n 

Ethylene  Oxide,  C3  H4  O.  This  substance  is  prepared  by 
the  action  of  potash  on  glycol  chlorhydrine,  which  loses  a 
molecule  of  hydrochloric  acid  and  forms  glycol  ether.  Ethy 
lene  oxide  is  a  volatile  colorless  liquid,  boiling  at  13-5,  soluble 
in  all  proportions  in  water.  It  does  not  form,  like  its  isomer 
aldehyde,  a  crystalline  compound  with  ammonia,  but  it  com 
bines  readily  with  hydrogen,  chlorine,  acids,  &c.  Alcohol, 
C2  He  O,  is  formed  by  the  direct  union  of  ethylene  oxide  with 
H2  ;  and  on  oxidation  glycolic  acid  is  produced. 

Polyethylene  Glycols  may  be  represented  as  bodies  con 
structed  on  the  type  of  3,  4,  5,  6,  &c.,  molecules  of  water  in 

which  several  molecules  of  C2  H4  are  substituted  for  the 
equivalent  of  hydrogen  ;  thus  we  have 


C2  H4 

Di-ethylene  Glycol,  C2  H4 
H2 


284 


Elementary  Chemistry. 


CaH4 

Tri-ethylene  Glycol,  C2  H4 
CaH4 


O4. 


CaH< 

C2  H4  f 

Tetra-Ethylene  Glycol,       "     \-  O5. 
L2  H4 

n 
CaH4 

Ha 

Ethylene  Diamines.  These  are  formed  on  the  type  of  two 
molecules  of  ammonia,  in  which  2,  4,  or  6  atoms  of  hydrogen 
are  replaced  by  ethylene.  We  thus  have  primary,  secondary, 
and  tertiary  dtanunes^  corresponding  to  the  monamines 
already  described.  They  are  volatile  bodies  obtained  by  the 
action  of  ammonia  on  ethylene  dibromide. 


HIGHER  DIATOMIC  ALCOHOLS  AND  DERIVATIVES. 

The  higher  carbon  series  yield  olefines  corresponding  to 
ethylene. 

The  following  is  a  complete  list  of  the  olefines  and  glycols, 
as  far  as  they  have  been  prepared  : 


Olefines. 


Ethylene 

Ca   H4 

Propylene 

C3    H6 

Butylene 

C4   H8       - 

h       3° 

Amylene 

C-5      HlO 

H     35° 

Hexylene 

Co      Hl3 

i-     69° 

Boiling  Point. 


Elementary  Chemistry. 


Boiling  Point. 

Heptylene 

C7   Hi* 

+      95° 

Octylene 

CTT 
8      -tll6 

+  116° 

Decatylene  \ 
(DiamyleneJ 

Cio  Hao 

~H    1  00° 

Cetene 

Ci.  H3a 

+  275° 

Cerotene 

Ca7    Hs4 

Melene 

Cao  Heo 

/ 


285 


Glycols. 

Ethyl  Glycol   C;2  **4   i  O 

Propyl  Glycol 

Butyl  Glycol      4  ^  8   I  O 

Amyl  Glycol 

Hexyl  Glycol 


C& 


C(1 


oa 

Boiling  Point. 

i97°-5 

oa 

188° 

oa 

183° 

Oa 

I77°* 

Oa 

207° 

Octyl  Glycol    v'8  ^  \  O9 


237° 


Each  of  these  combines  with  Cla  to  form  a  di-chloride,  and 
each  forms  a  glycol,  from  which  an  aldehyde  and  two  acids 
can  be  obtained  by  oxidation.  The  defines  above  ethylene 
yield  compounds  with  hydrochloric  and  hydriodic  acids,  which 
are  not  identical,  but  only  isomeric,  with  the  chlorides  and 
iodides  of  the  monatomic  radicals. 

*  We  have  here  to  notice  the  remarkable  exception  which  the  first  four  of  the 
glycols  exhibit  as  regards  their  boiling  points ;  in  opposition  to  the  general  law, 
the  higher  carbon  glycols  boil  at  a  lower  temperature  than  those  containing  less 
carbon. 


286  Elementary  Chemistry. 

LESSON  XXXIV. 

DIATOMIC  ACIDS,  RESULTING  FROM  THE  OXIDATION  OF 
THE  GLYCOLS. 

THESE  bodies  belong,  like   the  glycols,  to  the  type  of 
H  ) 
Ha  j  Oa>    There  are  two  series  of  these  acids,  the  first  derived 

by  the  replacement  of  2  atoms  of  hydrogen  in  the  ethylene 
by  i  atom  of  oxygen,  and  the  second  by  the  replacement  of 
all  4  atoms  of  hydrogen  in  ethylene  by  2  atoms  of  oxygen. 
The  first  of  these  groups  of  acids  may  be  termed  the  Lactic 
Acid  Series,  and  the  second  the  Oxalic  Acid  Series,  from  the 
substance  best  known  in  each.  The  relation  of  glycol  to 
glycolic  and  oxalic  acid,  serving  as  a  type  of  the  general  rela 
tions,  is  seen  in  the  following  :  — 

Glycol.  Glycolic  Acid.  Oxalic  Acid 


In  like  manner  we  have  the  following  series  of  acids  \— 
Type,  Cn  H2n_20    )  Q 

H2  f 

Name  of  Acid.  Lactic  Acid  Series. 

ii 

Carbonic  Acid    .     .     .  CO  )  ~ 
(Hydrate)  H2  \  °a' 

Glycolic  .  V-.  -,.  C'H'j°io,. 
Lactic.  . 


. 

H2 

Butylactic    .    .    .  C*  H"  °  1  Oa. 

rla  \ 


Elementary  Chemistry.  287 

Valero-lactic     .    .  C5  H8        O,. 


CflH100 
Leucic     .... 


Oxalic  Series  of  Acids. 
Type,Cn 


Ha 

Name  of  Acid.  Formula. 

Oxalic. 


Malonic. 

Succinic. 

Pyrotartaric. 

Adipic. 

(Unknown.) 

Suberic. 

Azelaic. 


c     1          .  Cio  Hie  O2 

Sebacic.  TT 

rl2 


Rocellic.  "  £ 

ii 
Carbonic  Acid,  C^  I  O>    This  substance  is  only  known 


288  Elementary  Chemistry. 

in  its  salts,  the  hydrate  not  having  been  prepared.     These 

ii 

salts  may  be  supposed  to  contain  the  radical  carbonyl,  CO. 
Carbonic  acid  contains  2  atoms  of  replaceable  hydrogen  ; 
hence  carbonates  of  the  following  composition  are  known  :  — 


Carbonic  Oxide,  C  O  (p.  76),  is  the  isolated  radical  car- 
bonyl  ;  this  substance  combines  directly  with  chlorine  to  form 

chlor-carbonyl  (phosgene  gas),  C  O  C12,  and  with  ^  I  O,  to 

form        £  v  O,  potassium  formate. 

ii 
Sulpho-Carbonic  Acid,     ^    (  S2.     The  potassium  salt  of 

this  acid  is  obtained  by  the  direct  combination  of  carbonic  di- 
sulphide  (page  116)  and  potassium  sulphide;  and  from  this 
salt  sulphocarbonic  acid  is  prepared  by  the  addition  of  hydro 
chloric  acid.  A  large  number  of  derivatives  of  this  body  are 

known:  thus  we  have  di-methyl  sulpho-carbonate,    //-TT  \  >  82; 

/-•c        ) 

hydric-methyl-sidpho-carbonate,    //-TT  \TT  \  Sa.       For    a    de 

scription  of  the  compounds  intermediate  between  the  sulpho- 
and  the  oxy-carbonates  the  larger  manuals  must  be  con 
sulted. 

The  acids  of  the  first  series  above  carbonic  are  monobasic, 
that  is,  they  have  only  one  atom  of  hydrogen  replaceable  by 
a  metal,  while  those  of  the  second  series  are  dibasic,  or  contain 
two  of  hydrogen  thus  replaceable  ;  both  series  are  diatomic. 

Glycolic  Acid,    2  (  O2.    This  substance  is  obtained  by 


the  oxidation  of  glycol  ;  it  may  also  be  derived  from  the  mon- 
atomic  series  of  acids  by  the  action  of  potash  on  mono-chlor- 
acetic  acid,  thus  : 


Elementary  Chemistry.  289 

Potassium  Mono-chlor  )  and  Potash  Potassium  Glycolate. 

Acetate,      j 

C2  H2  Cl  O  (  n      ,       H  )  ^          C2  H2  O 
K£U     T      : 

Glycolic  acid  forms  a  deliquescent  crystalline  mass,  and 
forms  salts  called  Glycolates,  which  contain  only  one  atom  of 
metal.  An  arnide,  called  Glycolamide,  is  known,  as  well  as  a 
substance  isomeric  with  it,  termed  Glycocolle. 

Oxalic  Acid,    Ca22  \  O2.     Oxalic  acid  is  met  with  in  the 


juice  of  many  plants  in  the  form  of  potassium  or  calcium  salt. 
It  is  formed  in  a  great  variety  of  ways,  chiefly  by  the  oxida 
tion  of  different  organic  bodies.  The  best  way  of  preparing 
pure  oxalic  acid  is  by  acting  upon  sugar  with  nitric  acid  ;  it 
has  generally  been  manufactured  in  this  way  on  a  large  scale, 
but  at  present  it  is  prepared  in  very  large  quantities  by  the 
action  of  caustic  potash  on  sawdust.  Crude  potassium  oxalate 
is  thus  formed,  and  from  this  a  pure  oxalic  acid  is  obtained  by 
precipitating  the  insoluble  calcium  oxalate  and  decomposing 
this  by  sulphuric  acid.  Oxalic  acid  can  also  be  prepared  by 
the  direct  oxidation  of  glycolic  acid. 

Oxalic  acid  crystallizes  in  prisms  which  possess  the  com 
position  C2  H2  O4  4-  2  Ha  O  ;  these  crystals  lose  their  water 
of  crystallization  at  100°,  or  in  vacua  over  sulphuric  acid. 
When  heated  to  about  160°  oxalic  acid  rapidly  decomposes, 
forming  carbonic  acid,  carbonic  oxide,  and  formic  acid,  whilst 
a  small  quantity  of  oxalic  acid  sublimes  undecomposed. 
Heated  with  sulphuric  acid,  oxalic  acid  is  decomposed  into 
water  and  equal  volumes  of  carbonic  acid  and  carbonic  oxide 
gases  (p.  76).  Oxalic  acid  is  a  bibasic  acid,  and  forms  two 
classes  of  salts  called  Hydric  Oxalates  and  Oxalates.  The 
alkaline  oxalates  are  all  soluble  in  water  ;  the  oxalates  of  the 
other  metals  are  generally  insoluble.  The  potassium  oxalates 
are  : 

C2  K2  O4  +  Ha  O.     Potassium  oxalate  (neutral  oxalate). 

C2  H  K  O4  +  H2  O.  Hydric  potassium  oxalate  (binox- 
alate). 

13 


290  Elementary  Chemistry. 

C2  H  K  O4  C2  H2  O4  4-  2  H2  O.  Acid  potassium  oxalate 
(quadroxalate). 

Calcium  oxalate  is  a  very  insoluble  salt,  and  is  the  form  in 
which  this  metal  is  obtained  for  quantitative  estimation. 
Methyl  and  ethyl  oxalates  are  obtained  by  distilling  the  re 
spective  alcohols  with  oxalic  acid  ;  the  first  boils  at  161°,  and 


has  the  formula  ,r*-}j\   f  O2 ;  the  second  boils  at  186°,  and 
(C  H3)2  J 

ii 

C"    O 

has  the  composition  ,~2 \j\ 
(C2  H5) 

Oxalic  Amides.      By  heating  neutral  ammonium  oxalate,  a 
white  powder  called  Oxamide  is  left ;  the  composition  of  this 


substance  is       H2  >  N2,  and  it  may  be  considered  as  being 
H2  ) 

2  molecules  of  ammonia,  in  which  2.  atoms  of  hydrogen  are 

ii 

replaced  by  C2  O2.     By  heating  hydric  ammonium  oxalate,  a 

substance  called  Oxamic  Acid  is  obtained,  having  the  formula 

H 


ii  belonging  to  a  mixed  type,  one  of  water  and  one  of 

C2  02  )  Q 
H     }U' 

ammonia,  in  each  of  which  one  atom  of  hydrogen  is  replaced 
by  the  dyad  C2  O2. 

Lactic  Acid.     3  -u-4       1  O2.     This  acid  is  contained  in  sour 
ri2       \ 

milk,  and  is  formed  from  sugar  by  a  peculiar  change  called 
the  Lactic  Fermentation  ;  an  acid  of  the  same  composition  is 
contained  in  the  flesh  of  animals  :  this  is,  however,  not  iden 
tical  with  that  obtained  by  the  fermentation  of  sugar,  —  hence 
the  former  is  termed  para-lactic-acid.  It  can  also  be  formed 
artificially  — 

(i.)  By  the  direct  oxidation  of  propyl  glycol. 


Elementary  Chemistry.  291 

(2.)  By  the  decomposition  of  mono-chlor  propionic  acid  by 
alkalies. 

(3.)  By  allowing  aldehyde,  hydrocyanic  acid,  and  hydro 
chloric  acid  to  remain  in  contact  for  several  days. 

C,  H4  O  +  H  C  N  +  H  Cl  2(H2  O)  =  N  H4  Cl  +  C3  H6  O,. 

Lactic  acid  is  a  syrupy  liquid  of  specific  gravity  i'2i5, 
which  cannot  be  distilled  without  decomposition,  but,  when 
heated,  forms  lactide  (the  anhydride),  C3  H,  O2,  and  dilactic 
acid,  C6  Hio  O5.  When  it  is  heated  with  hydriodic  acid, 
lactic  acid  forms  propionic  acid.  The  lactates  form  a  well- 
defined  class  of  salts,  containing  as  a  rule  one  atom  of  metal — 
the  other  atom  of  hydrogen  being  replaceable  only  by  an 

C3  H4  O  ) 

organic  radical :  thus  we  have  ethyl-lactic  acid,  C2  H5       >  O2, 

H        ) 

forming  also  a  definite  series  of  salts.  All  the  lactates  are 
soluble  in  water  and  alcohol  :  the  zinc  lactate  is  the  most 
characteristic  of  the  salts  ;  it  crystallizes  in  shining  needles. 

Lactyl  Chloride,  C3  H4  O  C12,  is  formed  by  the  action  of 
phosphorus  pentachloride  on  calcium  lactate. 

Lactamide,  C3  H7  O2  N  ;  lactic  monamide  is  obtained  by  the 
action  of  ammonia  on  lactide.  It  is  isomeric  with  alanine,  a 
substance  formed  by  the  union  of  aldehyde,  hydrocyanic  acid, 
and  water. 

The  higher  acids  of  the  lactic  series  do  not  possess  suffi 
cient  general  interest  to  entitle  them  to  consideration  in  an 
elementary  work.  We  therefore  pass  to  the  higher  acids  of 
the  oxalic  series. 

Malonic  Acid,  C3  H.,  O4,  is  obtained  by  the  oxidation  of 
malic  acid  (p.  293)  ;  it  is  an  unimportant  substance. 

Succinic  Acid,  C*  34  °2  I  O3.     This  acid  is  obtained  by 


H2 

the  distillation  of  amber  ;  it  occurs  in  certain  resins,  and  in 
small  quantities  in  various  animal  juices,  and  it  is  produced 
by  the  fermentation  of  sugar  (p.  308).  It  can  be  artificially 


292  Elementary  Chemistry. 

prepared  (i.)  by  the  action  of  hydriodic  acid  upon  malic  and 
tartaric  acids  (p.  293). 

(2.)  By  action  on  ethylene  di-cyanide  by  potash,  thus  : 

C2  H4  (CN)2  +  4  H.  O  =  C4  He  O4  +  2  NH3. 
(3.)  By  the  action  of  potash  on  cyanopropionic  acid,  thus  : 

C3  H5(CN)  Oa  +  2  Ha  O  =  C4  H6  O4  +  N  Hs. 
(4.)  By  the  action  of  nitric  acid  on  butyric  acid,  thus  : 
C4  H8  02  +  3  O  =  H2  O  +  C4  H6  04. 

Succinic  acid  forms  large  colorless  crystals,  which  fuse  at 
1 80°,  and  begin  to  boil  at  235°,  the  vapor  decomposing  into 
succinic  anhydride  and  water.  It  forms  a  chloride  as  well  as 
anhydride  when  heated  with  phosphorus  pentachloride. 
Bromine  substitution  products  are  also  known,  viz.,  mono- 

brom-succinic  acid,     4     3     r \^  ( O2,    and     di-brom-succinic 


acid,  c*H^Br202  )  ^  .    these    ^.^    when    treated    with 

water  and  silver  oxide,  are  respectively  converted  into  malic 
and  tartaric  acids.  Succinic  acid  forms  two  classes  of  salts, 
and  is  bibasic  ;  the  salts  of  the  alkaline  metals  are  soluble, 
and  these  form  an  insoluble  brown  precipitate  with  ferric 
salts. 

Succinic  Anhydride,  C4  H4  O3,  is  also  known. 

The  ammonia  derivatives  of  this  acid  are  : 

Succinamide,       H2       >-  N2,  and  Succinimide.^.^  H4  O2  >  N. 
H,     )  H       J 

For  the  special  properties  of  the  higher  carbon  acids  of 
this  series,  the  reader  must  consult  a  larger  work  on  the  sub 
ject. 

Connected  with  succinic  acid  very  intimately  are  two  acids 
of  much  importance,  viz.,  malic  and  tartaric  acids. 


Elementary  Chemistry.  293 

Malic  Acid,  C4  H6  O6.  This  acid  occurs  in  the  juice  of 
most  fruits,  from  which  it  can  be  obtained  ;  it  can  also  be 
prepared  by  the  substitution  of  H  O  for  Br  in  monobrom- 
succinic  acid  (p.  292).  Malic  is  a  triatomic  acid,  but  only 
two  of  the  three  typical  atoms  of  hydrogen  can  be  replaced 
by  metal  ;  hence  it  is  bibasic.  The  malates  are  soluble  in 
water ;  malic  acid  itself  crystallizes  in  needles.  When 
malic  acid  is  heated  to  about  180°  it  loses  H2  O,  and  is  con 
verted  into  a  new  acid,  C4  H4  O4,  which  exists  in  two  iso- 
meric  states,  forming  fumaric  and  maleic  acids.  These  sub 
stances  both  unite  directly  with  hydrogen  and  yield  succinic 
acid,  C4  H6  O4. 

Tartaric  Arid,  C4  H6  OB.  Tartaric  acid  exists  in  the  juice 
of  many  fruits  (grape,  tamarind,  &c.) ;  it  is  deposited  as  po 
tassium  salt  during  the  fermentation  of  wine,  and  this  salt  is 
known  as  tartar.  Several  interesting  isomeric  conditions  of 
tartaric  acid  exist ;  thus  the  ordinary  acid  possesses  the 
power  of  turning  the  plane  of  polarized  light  round  to  the 
right,  and  therefore  is  termed  Dextro-tartaric  acid,  whilst 
another  form  obtained  from  certain  specimens  of  tartar  does 
not  affect  the  ray  of  polarized  light  in  any  way,  and  is  said 
to  be  inactive.  This  inactive  tartaric  acid,  termed  Racemic 
Acid,  can  be  divided  into  the  common,  or  dextro-tartaric,  and 
a  new  acid  possessing  the  opposite  power  of  deviating  the 
plane  of  polarization  to  the  left,  and  hence  called  Levro-tar- 
taric  acid.  There  also  appears  to  be  a  fourth  modification 
of  this  acid  which  is  distinguished  by  being  inactive  like  ra- 
cemic,  but  not  capable  of  being  split  up  into  the  two  active 
varieties.  The  inactive  variety  of  tartaric  acid  can  be  pre 
pared  artificially  by  the  action  of  lime-water  on  bibromo-suc- 
cinic  acid,  C4  H4  Br2  O4,  each  of  the  atoms  of  bromine  being 
replaced  by  H  O,  and  yielding  tartaric  acid,  C4  H0  O6.  Tar 
taric  acid  is  also  formed  by  the  action  of  nitric  acid  on 
sugar  of  milk. 

Tartaric  acid  (dextro)  crystallizes  in  large  oblique  rhombic 
prisms  belonging  to  the  monoclinic  system,  which  dissolve 
easily  in  water.  When  heated  to  180°  it  fuses  and  undergoes 


294  Elementary  Chemistry. 

decomposition,  evolving  a  peculiar  odor  of  caramel.  In  pres 
ence  of  oxidizing  agents  tartaric  acid  is  converted  into  car 
bonic,  formic,  and  oxalic  acids  ;  and  when  fused  with  caustic 
potash  it  forms  acetic  and  oxalic  acids.  When  tartaric  acid 
is  heated  with  hydriodic  acid  for  several  hours  it  is  first 
reduced  to  malic,  and  afterwards  to  succinic  acid,  by  losing 
first  one  and  then  two  atoms  of  oxygen.  Tartaric  acid  is  a 
bibasic  acid,  containing  two  atoms  of  typical  hydrogen  which 
can  be  replaced  by  metals  ;  hence  there  are  two  classes  of 
alkaline  tartrates  ;  thus  we  have — 

Hydric  Potassium  Tartrate  )  ~    TT    vr. 
(Cream  of  Tartar)          f  Cl  Hs  K°8 

Potassium  Tartrate     .     .        C4  H4  K2  Oe. 

Tartaric  acid  forms  with  antimony  a  remarkable  compound 
termed  Tartar  Emetic ;  this  compound  may  be  considered 
as  potassium  tartrate,  in  which  one  atom  of  potassium  is 
replaced  by  a  monatomic  radical,  Sb  O.  We  then  have  tartar 
emetic,  C4  Ht  (Sb  O)  KO6.  This  body  is  obtained  by  boiling 
a  solution  of  cream  of  tartar  with  antimonious  oxide  ;  the 
oxide  dissolves,  and,  on  cooling,  tartar-emetic  is  deposited  in 
crystals.  This  salt  is  much  used  in  medicine,  and  acts  as  a 
violent  poison  when  taken  in  quantity.  Tartaric  acid  and 
citric  acid  are  largely  used  by  the  calico  printer  to  act  as  a 
discharge  or  solvent  for  the  mordant,  thus  giving  white  spots 
on  a  colored  ground. 

Citric  Acid,  C6  H8  Oi.  This  acid  is  tribasic,  and  it  is  found 
in  the  juice  of  the  lemon,  and  occurs  in  many  other  fruits, 
together  with  malic  acid.  Citric  acid  obtained  from  these 
sources  crystallizes  in  large  colorless  crystals,  which  dissolve 
very  easily  in  water.  Three  series  of  citrates  exist,  in  which 
one,  two,  or  three  atoms  of  hydrogen  are  replaced  by  metal. 
The  citrates  of  the  alkaline  metals  are  soluble,  those  of  the 
alkaline-earth  metals,  of  lead,  and  silver  are  insoluble  in 
water. 


Elementary  Chemistry.  295 

LESSON  XXXV. 

CYANOGEN  COMPOUNDS. 

We  have  already  seen  that  a  series  of  compounds  exists 
containing  a  monatomic  radical,  CN,  called  Cyanogen  ;  many 
of  these  compounds  may  be  arranged  under  the  three  types 
which  we  have  employed  for  other  organic  bodies.  Thus  we 
have 

Type   g  |  Type"  |  O. 

Hydrocyanic.^  Cyanic  Acid      C,? 


Acid        CN  j  J  H 

Cyanogen    CN  )  Sulpho-Cyanic  CN 

^        CN  Acid"  H 


Cyanogen    CN  ) 
Chloride        Cl  $ 

H)  CN) 

Type    H  \  N.  Cyanamide    H    \  N. 

H$  H    J 

The   cyanogen    compounds   may  also    be   considered    as 
derivatives  of  ammonia  ;  thus  cyanic  acid  acts  in  many  cases 
ii 

as  if  it  were      ^  (•  N,  and  this  group  becomes  connected  with 

the  oxalic  acid  series  of  bodies.     The  cyanogen  compounds 
are  remarkable  for  forming  series  ®i  polymeric  modifications  : 


thus  we  have  CN  Cl,  and  C3N3C13  ;  O,  and          3     O3. 

Cyanogen,   ^N  !•  .     This  substance  is  obtained  by  heating 

the  mercury,  gold,  or  silver  cyanides  ;  it  is  found  in  small 
quantities  in  the  gases  of  the  iron  blast  furnace.  Its  proper 
ties  have  already  been  mentioned  (p.  84.)  It  is  formed  by  the 
action  of  heat  on  oxamide,  and  ammonium  oxalate,  and  is 
thus  connected  with  the  oxalic  group,  as  cyanogen  is  oxamide, 


296  Elementary  Chemistry. 

minus  2  molecules  of  water.     Cyanogen  forms  with  potash  a 
mixture  of  potassium  cyanide  and  cyanate. 

Hydrocyanic  Acid,  HCN.  The  mode  of  preparation  and 
chief  properties  of  this  substance  have  already  been  men 
tioned.  This  acid  easily  undergoes  decomposition,  and  can 
not  therefore  be  kept  for  a  length  of  time  either  in  the  pure 
state  or  in  aqueous  solution.  It  yields  ammonium  formate 


thus:   HCN  +  2  H2  O  =  O,  as  methyl  cyanide  yields 

acetic  acid  (p.  252).  With  chlorine  and  bromine  it  yields 
cyanogen  chloride  and  bromide.  The  best  method  of  de 
tecting  hydrocyanic  acid  is  founded  on  the  formation  of  Prus 
sian  blue.  To  the  liquid  containing  the  acid  a  few  drops  of  a 
ferrous  and  a  ferric  salt  are  added  ;  then  excess  of  caustic 
soda  ;  and  lastly,  an  excess  of  hydrochloric  acid,  the  forma 
tion  of  a  deep  blue  liquid,  from  which  a  deep  blue  precipitate 
separates  either  at  once  or  after  a  little  time,  indicates  the 
presence  of  hydrocyanic  acid.  The  presence  of  this  substance 
may  also  be  recognized  by  evaporating  some  of  the  solution 
on  a  watch  glass  with  ammonium  sulphide  to  dryness  on  a 
water-bath  ;  on  adding  a  drop  of  ferric  chloride,  a  deep  red 
coloration  of  ferric  sulpho-cyanide  is  produced,  if  hydrocyanic 
acid  be  present. 

The  simple  metallic  Cyanides  are  formed  by  the  direct 
action  of  hydrocyanic  acid  upon  a  metallic  oxide  ;  in  addition 
to  these  a  large  number  of  double  Cyanides  are  known. 

Potassium  Cyanide,  KCN,  is  formed  when  potassium  is 
burnt  in  cyanogen  or  in  hydrocyanic  acid  gas,  or  when  potash 
is  added  to  aqueous  hydrocyanic  acid.  It  is  prepared  on  a 
large  scale  by  fusing  potassium  ferro-cyanide  (p.  297)  with 
potassium  carbonate.  The  iron  is  thus  separated,  and  potas 
sium  takes  its  place.  Potassium  cyanide  is  a  white  salt,  very 
soluble  in  water  and  hot  alcohol  ;  it  fuses  easily  without  de 
composition,  and  acts  as  a  violent  poison.  Potassium  cyanide 
is  largely  used  in  photography  for  dissolving  the  unaltered 
silver  salts  ;  also  in  still  greater  quantity  in  the  art  of  electro- 
typing  in  gold  and  silver,  serving  as  a  solvent  for  these  metals. 


Elementary  Chemistry.  297 

The  sodium  and  ammonium  cyanides  are  also  soluble,  very 
poisonous  salts. 

Mercuric  Cyanide,  Hg  C2  N3,  is  a  soluble,  easily  crystal- 
lizable  salt,  formed  by  dissolving  mercuric  oxide  in  aqueous 
hydrocyanic  acid.  When  heated  it  decomposes  into  gaseous 
cyanogen  (CaNs),  mercury,  and  a  brown  substance,  isomeric 
with  cyanogen  gas,  and  called  Paracyanogen. 

The  other  simple  cyanides  are  insoluble  in  water ;  amongst 
the  most  important  is  the  white  silver  cyanide,  and  the 
brownish-red  copper  cyanide.  In  writing  the  formulas  of  these 
compounds,  it  is  useful  to  express  cyanogen  by  the  symbol 
Cv.  Amongst  the  numerous  compound  cyanides,  those  of 
potassium  and  iron  are  the  most  important  ;  in  these  the  iron 
is  contained  in  combination  in  a  different  mode  to  that  in  the 
ordinary  iron  salts,  inasmuch  as  it  is  not  precipitated  from 
the  cyanide  solution  by  such  re-agents  as  ammonia,  or  am 
monium  sulphide.  The  same  remark  applies  to  cobalt,  and 
in  a  less  degree  to  several  other  metals. 

Potassium  Ferrocyanide,  K4FeCy6.  This  salt,  commonly 
called  yellow  prussiate  of  potash,  is  made  on  a  large  scale  by 
heating  nitrogenous  organic  matter  with  potashes  and  iron 
filings.  On  dissolving  the  mass  in  water,  and  evaporating 
the  solution,  large  yellow  quadratic  crystals  of  potassium  fer- 
rocyanide,  containing  3  atoms  of  water  of  crystallization,  are 
deposited  ;  it  is  not  poisonous,  acting  as  a  mild  purgative. 
When  heated  strongly,  it  yields  potassium  cyanide  and  iron 
carbide,  and  when  treated  with  dilute  sulphuric  acid,  hydro 
cyanic  acid  is  formed.  By  the  action  of  strong  and  hot  sul 
phuric  acid,  the  salt  is  decomposed,  and  carbonic  oxide  gas 
evolved.  Solutions  of  this  salt  produce  with  ferric  salts,  a 
deep  blue  precipitate  of  Prussian  blue,  a  ferric-ferrocyanide 
having  the  composition  Fe4(FeCy8)3.  With  ferrous  salts  the 
yellow  precipitate  produces  a  white  precipitate. 

Hydric  Ferrocyanide,  or  Ferrocyanic  Acid,  H4  Fe  Cy0. 
This  acid  is  formed  by  adding  hydrochloric  acid  to  a  strong 
solution  of  the  foregoing  salt.  It  acts  as  a  strong  acid,  and  is 
tetrabasic,  forming  a  series  of  salts  in  which  the  four  typical 

13* 


298  Elementary  Chemistry. 


atoms  of  hydrogen  of  the  acid  are  replaced  by  an  equivalent 
of  metal. 

Potassium  Ferricyanide,  K3  Fe  Cy6.  This  salt,  called  red 
prussiate  of  potash,  is  obtained  by  passing  chlorine  gas 
through  a  solution  of  the  yellow  prussiate,  which  loses  one 
atom  of  potassium  ;  the  action  must  be  allowed  to  continue 
until  a  drop  of  solution  produces  no  blue  precipitate  with  a 
ferric  salt.  On  evaporation,  the  salt  separates  out  in  deep 
red  prismatic  crystals.  This  substance  produces  in  solutions 
of  ferrous  salts  a  deep  blue  precipitate  of  Turnbull's  blue, 

Fe5  Cyia 
Fe3(FeCy6)2. 

Nitro-Ferrocyanides  are  a  peculiar  class  of  salts,  obtained 
by  the  action  of  nitric  acid  on  potassium  ferro  cyanide.  The 
sodium  salt  crystallizes  in  red  prisms,  and  produces  with  the 
slightest  trace  of  an  alkaline  sulphide  a  deep  purple  color. 

Cyanogen  Chlorides.  Cyanogen  forms  with  chlorine  a 
chloride  which  exists  in  3  polymeric  modifications  ;  they  are 
all  obtained  by  the  action  of  chlorine  upon  hydro-cyanic  acid. 

Boiling      Melting 
Point        Point. 

Gaseous  Cyanogen  Chloride  .     Cy   Cl    —   12°       -  15° 
Liquid.     .     . Cy2  Cl*         I5°'5          o° 

Solid    .     .   ••."-'.  "".     .     .     .     .     Cy,  Cli  190°       140° 

Cyanic  Acid,  iff  O.     The  salts  of  this  acid,  termed  cyan- 

ates,  are  readily  formed  by  the  direct  oxidation  of  cyanides, 
and  by  the  action  of  cyanogen  gas  upon  potash.  Cyanic  acid 
itself  cannot  be  prepared  in  the  free  state  from  its  salts,  as  on 
liberation  it  at  once  changes  into  polymeric  modifications 
called  cyanuric  acid  and  cyamelide.  It  can,  however,  be 
obtained  by  heating  cyanuric  acid  in  a  retort,  and  collecting 
the  volatile  cyanic  acid  in  a  freezing  mixture  ;  it  forms  a 
colorless  mobile  liquid,  but  it  immediately  changes  into  solid 
cyamelide  when  taken  out  of  the  freezing  mixture.  Cyanic 
acid  in  aqueous  solution  combines  at  once  with  water  to  form 


Elementary  Chemistry.  299 

ammonium  carbonate,          !•  O  +  H4  O2  =  NH4  H  CO3,  and 

CN  ) 
with  ammonia  to  form  urea,      ^  [•  O  -f  NH3  =  CO  N2  H4. 

Cyanic  acid  is  a  monobasic  acid. 

CN    ) 
Ammonium   Cyanate^  ^TTT    >•  O,  is  formed  by  bringing  to 


gether  dry  ammonia  and  cyanic  acid  ;  but  this  salt  under 
goes  gradually  at  ordinary  temperatures,  and  at  once  at  100°, 
a  remarkable  molecular  change,  becoming 


CN    )  C0 

£S    f  O  =      H,  V  N2. 

NH*  >  Ha  J 


CO} 

Urea,  or  Carbamide.   H2  >  N2.     This  important  substance 

.HO 

is  found  in  large  quantity  in  the  urine  of  mammalia,  and  in 
small  amount  in  various  animal  juices.  It  is  obtained  arti 
ficially — (i.)  From  ammonium  cyanate, 

4>         s> 

CN  NH4  O  =   u   <•  ™    f  • 


NX          "  S  *i  S 

v  •  -%  >    */v      Sf 

(2.)  By  the  action  of  ammonia  on  ethyl  carbonate,  thus  • 

J  > 


rn        )  2  r    H 

°2  +  Hs     N2  =    H2    'Na  +  2 


Ethyl  Carbonate.  Urea.  Alcohol. 

(3.)  By  the  action  of  mercuric  oxide  on  oxamide  : 

ii  a 

C2  02  )  CO  ) 

H2  \  N2  +  Hg  O  =  H2  \  N2  +  CO.  +  Hg. 
Ha  \  H2  ) 

Oxamide.  Carbamide. 


300  Elementary  Chemistry. 

The  first  of  these  methods  is  that  by  which  urea  is  best  pre 
pared.  For  this  purpose  yellow  prussiate  of  potash  is  mixed 
with  manganese  dioxide,  and  the  mixture  heated  on  an  iron 
plate  ;  potassium  cyanate  is  thus  formed,  and  this  salt  is  dis 
solved  in  water  and  mixed  with  ammonium  sulphate.  On 
evaporating  to  dryness  the  urea  can  be  extracted  with  alco 
hol.  Urea  thus  prepared  crystallizes  in  long  striated  needles, 
which  dissolve  in  their  own  weight  of  cold  water,  and  to  the 
same  extent  in  hot  alcohol.  When  heated  to  120°,  urea  fuses 
and  begins  to  decompose,  forming  substances  termed  amme- 
line  and  biuret ;  whilst  at  a  higher  temperature  cyanuric  acid 
is  produced.  When  heated  with  water  in  closed  tubes  to 
1 00°,  urea  forms  carbonic  acid  and  ammonia,  showing  that  it 
is  an  amide  of  carbonic  acid.  Nitrcus  acid  decomposes  urea 
instantly  into  carbonic  acid,  nitrogen,  and  water.  Urea  is 
the  product  of  the  oxidation  of  the  nitrogenous  constituents 
of  the  body,  and  the  quantity  of  urea  excreted  is  a  measure  of 
the  activity  of  the  changes  going  on.  Urea  forms  com 
pounds  with  acids  and  with  bases.  Urea  nitrate  and  oxalate 
are  the  most  important  salts.  With  mercuric  oxide,  urea 
forms  an  important  insoluble  compound,  which  is  employed 
as  a  means  of  estimating  the  quantity  of  urea  in  a  solution. 

Compound  Ureas.  These  compounds  are  formed  by  acting 
on  cyanic  acid  with  a  compound  ammonia.  They  may  be 
considered  as  urea,  in  which  one  or  more  atoms  of  hydrogen 
are  replaced  by  methyl,  ethyl,  &c.  Compound  ureas,  con 
taining  the  oxidized  radicals,  acetyl,  butyryl,  &c.,  are  also 
known. 

Cyanuric  Acid,   -X3  v  O3.     This  polymer  of  cyanic  acid  is  a 

solid  crystalline  substance  formed  on  heating  urea,  or  by 
acting  with  water  on  the  solid  cyanogen  chloride.  It  is  a 
tribasic  acid,  and  is  formed  on  the  type  of  3  molecules  of 
water. 

Sulphocyanic  Acid,  ,T  [  S.  The  potassium  salt  of  this 
acid  is  easily  prepared  by  heating  potassium  ferrocyanide 


Elementary  Chemistry.  301 

with  sulphur  ;  on  dissolving  and  crystallizing,  potassium  sul- 
phocyanide,  j7  [  S,  is  deposited.  The  acid  may  be  obtained 

by  acting  on  mercuric  sulphocyanide  with  sulphuretted  hy 
drogen. 

CN )  CN } 

Cyanamide,    H    >•  N  ;    Dicyanamide,  CN  J-  N  ;    and     Tri- 

H    }  H) 

CN) 
cyanamide,  CN  >  N,  are  obtained  by  the  action  of  ammonia 

CN$ 

on  cyanogen  chloride.  Several  other  amidic  compounds  of 
cyanogen  exist,  for  description  of  which  the  larger  manuals 
must  be  consulted. 

Uric  Acid,  C5  H4  N4  O3.  This  substance,  found  in  the 
urine  of  birds,  serpents,  &c.,  is  connected  with  the  foregoing 
compounds.  From  uric  acid  a  large  number  of  derivatives 
have  been  obtained,  amongst  which  may  be  named  alloxan, 
C4  H2  N2  O4  ;  dialuric  acid,  C4  H4  N2  O4  ;  alloxatine,  C8  H4 
N4  OT  ;  and  parabanic  acid,  Cs  H2  N2  O3  :  these  derivatives 
of  uric  acid  can  be  generally  regarded  as  amides,  containing 
the  radical,  C2  O2,  of  oxalic  acid. 


LESSON   XXXVI. 

TRIATOMIC   ALCOHOLS  AND  THEIR   DERIVATIVES. 

THE  hydrocarbon  group  having  the  general  formula  Cn 
H2l—  i,  act  in  accordance  with  the  views  already  expressed 
(p.  231)  as  triatomic  radicals,  to  which  the  generic  name  of 
Glycerines  has  been  given  from  the  special  name  of  one  of 


the  series,  viz.  C3H5  >  O3.     This   substance  is  arranged  on 

H3$ 
the  type  of  3  molecules  of  water,  and  contains  3  atoms  of 


3O2  Elementary  Chemistry. 

typical  hydrogen,  each  replaceable  by  a  metal.  From  this 
formula  it  is  clear  that  the  possible  number  of  derivatives  of 
the  triatomic  alcohols  is  much  larger  than  that  of  either  of  the 
preceding  classes.  The  relation  existing  between  the  com 
position  of  the  mono-,  di-,  and  triatomic  alcohols  of  the  same 
carbon  series  is  a  very  simple  one,  as  is  seen  by  the  follow 
ing  comparison  of  the  three  carbon  series  : 

C   H    ) 
Monatomic  propyl-alcohol       3  jr7  >  O,  or  C3  H8  O. 

ii      ) 

Diatomic  propyl-glycol,         C3  H3  >  O2,  or  C3  H8  Oa. 

H;  \ 


Triatomic  propyl-glycerine,  C3  H5  >  O3,  or  C3  H8  O3. 

The  glycerines  of  the  mono-  and  dicarbon  series  have  not 
been  prepared  ;  that  of  the  tri-carbon  series  is  best  known 
and  may  be  taken  as  the  type  ;  amyl  glycerine  has  also  been 
prepared. 

Glycerine,  C3H6  >  O3.     This  substance,  is  contained  in  most 


in   ) 

,H6f.  03. 

H3 


oils  and  fats,  both  vegetable  and  animal,  which  consist  of 
triatomic  ethers  of  the  higher  terms  of  the  fatty  acid  series  ; 
thus  beef  suet,  or  stearine,  is  glycerine  tri-stearate,  or  gly 
cerine  in  which  the  3  atoms  of  typical  hydrogen  have  been 
replaced  by  3  molecules  of  the  radical,  Ci*  H3B  O,  of  stearic 
acid  (p.  249).  Glycerine  is  also  found  in  small  quantities  in 
the  fermentation  of  sugar.  Glycerine  is  formed  from  fats  by 
the  process  of  saponification,  or  treatment  of  the  oil  with 
caustic  alkali,  which  decomposes  the  compound  forming  an 
alkaline  stearate  (soap),  and  liberating  the  glycerine  which 
remains  in  solution  when  the  soap  is  separated  by  throwing  in 
common  salt.  In  order  to  obtain  pure  glycerine  the  fat  may 
be  decomposed  by  lead  oxide  ;  the  glycerine  remains  in  solu 
tion,  and  the  lead-soap  or  plaister  is  precipitated.  Another 


Elementary  Chemistry.  303 

and  better  method  is  to  decompose  the  fats  with  high  pres 
sure  steam,  free  stearic  acid  and  glycerine  being  produced. 

Glycerine  is  a  colorless  thick  syrupy  liquid,  of  specific 
gravity  i'28  ;  it  possesses  a  very  sweet  taste  (whence  its 
name),  and  is  soluble  in  water  and  alcohol.  It  can  be  dis 
tilled  in  presence  of  aqueous  vapor  and  in  vacua,  but  it  under 
goes  decomposition  when  heated  in  the  air.  When  mixed 
with  dilute  nitric  acid,  glycerine  undergoes  oxidation  and 

forms  glycerinic  acicf,      3  ^ 3       (•  O3,  by  exchange  of  H2  for  O ; 

this  acid,  therefore,  stands  to  glycerine  as  acetic  acid  does  to 
ethyl  alcohol.  Glycerine  is  reduced  by  hydriodic  acid  to  iso- 
propyl  iodide,  thus  : 

Glycerine.  Iso-propyl  Iodide. 

C3  H8  03  +  5  H  I  =  C3  H7  I  +  2  I,  +  3  H2  O. 

Propylglycol  is  also  reduced  to  the  same  substance,  and  thus 
we  can  pass  from  the  di-  and  triatomic  series  of  alcohols  to 
the  monatomic  series  of  iso-alcohols. 

If  the  nitric  acid  employed  to  act  on  glycerine  be  concen 
trated,  a  new  compound  called  Trinitrine,  or  Trinitro-gly- 
cerine,  is  formed  ;  this  is  glycerine  in  which  the  3  atoms  of 

/->     TT          ~\ 

typical  hydrogen  are  replaced  by  N  O*  ;  thus,  -/jJoJ)  r  O«. 
This  substance  explodes  violently  when  heated,  and  it  is  pro 
posed  to  use  it  for  blasting  and  other  purposes.  Heated 
with  hydrochloric  acid,  glycerine  forms  compounds  termed 
Chlorhydrines.  These  substances,  of  which  there  are  three. 
are  formed  upon  the  mixed  type  of  water  and  hydrochloric 
acid  ;  their  composition  will  be  easily  understood  by  the 
following — 

Types. 

Ha(    r\  H  \  f>. 

8  H.?0*  H>°  HaCl8. 

H  Cl  H2C1,. 


304  Elementary  Chemistry. 

Glycerine.  Chlorhydrine.          Dichlorhyclrine.          Trichlorhydrine. 

C3  H5 )  o          m    j.     ,2'       m      (.  Q  C3  H6  C13. 

n>  ^3.     p.  TT    \  LI.      r*   M    \ 
3        )  L,3li5   '  L3    il5    ' 

Similar  compounds  are  formed  with  bromine. 

The  Acetic  Ethers  of  Glycerine,  or  Ace  tines,  are  some  of 
the  best-known  compounds  of  this  alcohol ;  of  these  there  are 
three,  viz.  : 

Mono-acetine.  Di-acetine.  Tri-acetine. 

CTT  )  /"•        T_T  }  r*        TT 

s  rls         /  (^  L3  rla          (  n  L3  .tt.5          (  n 

(C2H3OjH2  f  u        2(C2  H3  O)  H  f  u          3(C4  H3  O)  f  u 

These  substances,  which  resemble  the  fats  in  constitution,  are 
obtained  by  acting  upon  glycerine  with  glacial  acetic  acid. 
They  are  thick  oily  liquids,  only  sparingly  soluble  in  water, 
and  boiling  at  a  high  temperature. 

The  Stearic-,  Palmitic-,  and  Oleic  Ethers  of  Glycerine,  or 
Stearines,  Palmitines,  and  Oleines,  are  of  great  importance, 
as  forming  the  natural  fats.  The  stearines  may  be  prepared 
artificially  by  heating  glycerine  with  stearic  acid. 

Monostearine.  Distearine.  Tristearine. 

/-«        TT  \  r^TT  \  /""T_T 

(Ci8  H38  C))  H2  |  °3'   2(C183H3550)  H  [  °3'   3(C183H36'  ( 

Tri-stearine  can  be  obtained  by  melting  beef  or  mutton 
suet,  and  separating  the  fibrous  matter  by  filtration  and  crys 
tallizing  the  stearine  from  solution  in  hot  ether.  It  forms 
bright  white  shining  plates,  insoluble  in  alcohol  and  water,  but 
readily  soluble  in  ether.  The  melting  point  of  stearine  appears 
to  undergo  changes,  and  hence  it  is  probable  that  this  sub 
stance  is  capable  of  existing  in  several  distinct  modifications. 

Similar  glycerine-ethers  have  been  prepared  with  many  of 
the  other  members  of  the  series  of  fatty  acids.  By  the  action 
of  the  mono-,  di-,  and  tri-chlorhydrines  upon  sodium  ethylate, 
the  three  ethyl-glycerine  ethers,  or  ethylines,  have  been  pre 
pared  ;  these  are — 


Elementary  Chemistry.  305 

Ethyline.  Di-ethyline.  Tri-ethyline. 

Cs  H5      \  f^  C3  H5       )  ft  C3  H5     \  ft 

(C2H6)  Ha  f  °3'       2  (C,  H5)H  f  U  3  (C,  H.)  )  U 

Poly -glycerines  are  known,  corresponding  to  the  polyatomic 
glycols  (p.  283).  Thus  we  have  — 

C-3    -H-6   )  C-3-H-6 

Di-glycerine,  C3  Hs  >-  O6.          Tri-glycerine  C3H6 
H4j  C3H5 

H6 

Natural  Fats  and  Oils.  The  natural  oils  and  fats  are  all 
compounds  of  glycerine  chiefly  with  palmitic,  oleic,  or  stearic 
acids,  and  they  are  contained  in  the  bodies  both  of  plants  and 
animals.  The  fats  cannot  be  distilled  without  decomposition, 
and  when  heated,  give  rise  to  a  powerfully  smelling  substance 
called  acroleine  (p.  306).  The  oils  are  separated  into  the  dry 
ing  and  non-drying ;  the  former  become  dry  and  resinous  on 
exposure  to  air  from  oxidation,  whilst  the  others  remain 
unaltered.  The  drying  oils  are  generally  glycerides  of  acids 
not  belonging,  but  nearly  related,  to  the  fatty  acid  series  ; 
such,  for  instance,  is  the  acid  of  linseed  oil,  called  linoleic 
acid,  Cia  H28  Oa :  oleic  acid,  Cis  H34  O2,  is  found  in  almost 
all  oils  and  fats,  the  compound  of  this  acid  with  glycerine  con 
stituting  the  liquid  portions  of  the  fats. 

When  the  oils  or  fats  are  acted  upon  by  nitric  acid  they 
are  decomposed,  and  the  series  of  fatty  acids  formed.  Fatty 
bodies  when  boiled  with  alkali  undergo  the  remarkable 
change  termed  Saponification  (p.  302)  ;  the  fat  is  decom 
posed  into  a  fatty  acid  which  combines  with  the  alkali,  and 
glycerine  which  is  liberated  passes  into  solution.  Fats  may 
also  be  saponified  or  separated  into  acid  and  glycerine  by  dis 
tillation  with  steam  alone. 

Ally  I  Compounds.  Intimately  connected  with  glycerine 
are  the  compounds  of  a  monatomic  radical,  Ca  H5,  called 
allyl.  By  the  action  of  phosphorus  iodide  upon  glycerine, 
a  monatomic  iodide.  C3  H8 1,  is  obtained,  from  which  a  num 
ber  of  bodies  have  been  derived,  whilst  the  acrid  substance 


306  Elementary  Chemistry. 

acroleine  formed  in  the  destructive  distillation  of  glycerine  is 
the  aldehyde  of  this  series. 

C  W    I 

Ally  I  Alcohol,      3  TTB  [•  O,  obtaining  by  acting  with  ammo 

nia  on  allyl  oxalate. 


1  Allyl  oxalate  and  ammonia  yield  oxamide  and  allyl  alcohol. 
It  is  a  colorless  liquid,  boiling  at  103°,  possessing  a 
pungent  smell.  It  is  oxidized  in  presence  of  air  and  plati 
num  to  acroleine  and  acrylic  acid,  which  stand  to  this  alco 
hol  in  the  same  relation  as  aldehyde  and  acetic  acid  stand  to 

C*    T-f    O  ) 

ethyl   alcohol;    thus   acroleine  is     8  -rr3       [and  acrylic  acid 

\  O.      Sodium   dissolves   in   allyl  alcohol,  forming 

sodium  allylate,  one  atom  of  typical  hydrogen  in  the  al 
cohol  being  replaced  by  sodium  ;  when  this  substance  acts 
upon  allyl  iodide,  an  exchange  of  allyl  and  sodium  takes 

place,  allyl  ether,     *     '  -  O,  being  formed.      The  allyl  sul- 


(~*    T-T    ") 

phide,  rz  Tj5  [•  S,  is  remarkable  as  occurring  in  nature  as  the 

v-3  -M.  5  y 

essential  oil  of  garlic,  and  the  sulphide  artificially  prepared 
is  identical  in  properties  with  the  natural  essence.     In  like 

C*   T-T    ") 

manner,  allyl  sulphocyanide,     J,  ^  >  S,  is  found  as  the  essen 

tial  oil  of  black  mustard  seed. 


TETRATOMIC  ALCOHOLS  AND  THEIR  DERIVATIVES. 

Tartaric  and  citric  acids  are  tetratomic,  but  the  former  is 
bibasic  and  the  latter  tribasic.  The  only  tetratomic  alcohol 
as  yet  known  is  erythrite,  a  substance  found  in  certain 
lichens  and  fungi ;  its  composition  is  C4  Hio  (X,  or  it  may  be 


Elementary  Chemistry.  307 

TT        \ 

represented  at  ^     [  O4,  in  which   four  of  hydrogen  are  re- 

IV 

placed  by  the  tetratomic  radical  C4  H6.  Treated  with  hy- 
driodic  acid,  erythrite  forms  iso-butyl  iodide.  The  relations 
of  these  tetratomic  compounds  is  seen  by  the  following  for 
mula  : 

IV 


Erythrite,  C<H"'  |  O,.       Tartaric  acid,0^"^*  1  O.. 
Citric  acid,  C^°3  |  O, 

HEXATOMIC  ALCOHOLS  AND  THEIR  DERIVATIVES. 

The    best-defined    member    of   this    series    is    mannite, 
C6  Hu  O6,   which    may    be   considered  as   6  molecules   of 

H    ) 
water,  „*  >  O6,  in  which  6  atoms  of  hydrogen  are  replaced 

by  a  hexatomic  radical,  C6  H8.  Mannite  is  a  solid,  sugar- 
like  substance  contained  in  manna,  the  exudation  from 
several  species  of  ash.  Mannite  can  be  artificially  prepared 
from  certain  varieties  of  sugar,  which  take  up  H2  when 
treated  with  water  and  sodium  amalgam,  C6  Hi2  O5  +  H2  = 
C6  Hi4  O6.  By  oxidation  of  mannite,  the  reverse  change 
occurs,  and  a  fermentable  sugar,  C6  Hi2  O8,  is  produced  :  this 
change  can  also  be  effected  by  a  peculiar  ferment.  The  chief 
reasons  for  giving  a  hexatomic  character  to  mannite  are,  (i) 
that  when  this  substance  is  acted  on  by  nitric  acid,  a  com 
pound,  called  nitro-mannite,  is  formed,  which  is  mannite  con 
taining  the  6  typical  atoms  of  hydrogen,  replaced  by  NO2  : 


thus  its  composition  is  C6  H8    >•  O6,  and  it  is  to  be  regarded 

6(NO*)) 

not  as  a  substitution  product,  but  as  the  nitrate  of  a  hexatomic 
radical,  which  corresponds  to  ethyl  nitrate  in  the  monatomic 
series  :  (2)  that  mannite  is  attacked  by  hydriodic  acid  in  a 


308  Elementary  Chemistry. 

similar  manner  to  glycerine  (p.  302),  and  erythrite  (p.  306), 
the  monatomic  iodide  of  the  same  number  of  carbon  atoms 
being  formed  ;  thus  we  have 

C6  H14  O8  +  ii  H  I  =  C6  Hi,  I  4-  5  Ia  +  6  H2  O. 

Mannite  Jso-hexyl 

Iodide. 

In  like  manner  the  6  of  hydrogen  can  be  replaced  by  6  atoms 
of  the  radical  of  stearic  acid  ;  we  have  then  a  compound 

VI  ) 

mannite  hexastearate,        CeH8       >  Oa. 

6(C18H36O)  ) 

The  substances  having  the  composition  of  the  iodides  of 
the  monatomic  radicals,  and  obtained  by  deoxidation  from 
glycerine  (p.  302),  erythrite  (p.  306),  and  mannite,  are  isomeric, 
and  not  identical  with  these  iodides  ;  they  may  be  considered 
to  be  compounds  of  the  olefine  with  hydriodic  acid.  By  the 
action  of  silver  oxide  and  water,  the  bodies  yield  a  hydrate 
having  the  composition  of  the  monatomic  alcohols,  but  differ 
ing  from  these  in  their  boiling  points,  and  in  their  chemical 
relations  ;  thus  these  so-called  iso-alcohols  readily  yield  the 
olefines  from  which  they  are  derived,  and,  on  oxidation,  do 
not  produce  the  corresponding  acid,  but  form  an  acetone  by 
loss  of  hydrogen  ;  indeed  these  iso-alcohols  can  be  obtained 
by  the  action  of  hydrogen  upon  the  acetones,  thus — 

C3H8O  +  H2  =  C3H8O2. 

Acetone.  Iso-propyl  alcohol. 


LESSON   XXXVII. 

SACCHARINE  BODIES. 

THESE  substances  are  frequently  termed  carbo-hydrates,  in 
asmuch  as  they  contain  hydrogen  and  oxygen  in  the  propor 
tion  to  form  water,  united  with  carbon.  They  form  an  im- 


Elementary  Chemistry. 


309 


portant  class  of  substances  as  occurring  widely  diffused  in  the 
bodies  of  plants.  They  may  be  divided  into  three  classes  : 
(i)  Sucroses,  or  the  sugars  proper  ;  (2)  Glucoses,  or  the  grape 
sugars  ;  (3)  Amyloses,  or  starch  and  woody  fibre. 

Each  of  these  three  classes  contain  several  distinct  sub 
stances. 


I.  Sucroses. 

2.  Glucoses. 

3.  Amyloses. 

CiaHaaOn. 

C6H1206. 

C6H1005. 

Sucrose  + 

Dextrose  4- 

Starch  + 

(or  cane  sugar). 

(or  grape  sugar). 

Glycogene  -f 

Lactose  -4- 

Levulose  — 

Dextrine  + 

(or  milk  sugar). 

(or  fruit  sugar). 

Inuline  — 

(      Melitose      J 

Gums. 

<    Melezitose    >  + 

Galactose.  — 

Cellulose. 

(      Mycose.      ) 

Tunicine. 

The  most  important  distinguishing  physical  property  of 
these  bodies  is  their  action  on  polarized  light.  Like  tartaric 
acid  (p.  293),  and  many  other  substances,  these  saccharine 
bodies  possess  the  power  of  turning  the  plane  of  polarization, 
some  to  the  right-hand  and  some  to  the  left :  thus  dextrose, 
or  grape  sugar,  turns  it  to  the  right,  levulose,  or  fruit  sugar,  to 
the  left.  The  right-handed  substances  are  marked  in  the 
preceding  list  with  a  +,  the  left-handed  with  a  — . 

SUCROSES.  Sucrose,  or  Cane  Sugar,  CiaHaaOn. — This  im 
portant  substance  occurs  in  the  juice  of  certain  plants,  espe 
cially  the  sugar-cane,  beetroot,  mallow,  and  sugar-maple ; 
also,  in  smaller  quantity,  in  honey  and  various  kinds  of  fruit, 
together  with  a  mixture  of  dextrose  and  levulose.  Sugar  is 
prepared  from  the  sugar-cane,  which  contains  about  18  per 
cent,  of  sugar,  by  crushing  out  the  juice  by  passing  the  cane 
between  rollers  ;  the  juice  is  at  once  heated  to  about  60°,  and 
a  small  quantity  of  milk  of  lime  added  for  the  purpose  of 
precipitating  the  albuminous  matter  derived  from  the  cane,  the 
presence  of  which  renders  the  juice  liable  to  quick  fermenta 
tion.  The  juice  is  then  raised  to  the  boiling  point,  the  scum 


3IO  Elementary  Chemistry. 

which  rises  to  the  surface  removed,  and  the  clear  liquid 
remaining  is  boiled  down  in  copper  pans  until  it  attains  a 
certain  consistence,  when  it  is  filtered  through  linen  bags,  and 
again  evaporated  to  a  syrup,  which,  on  cooling,  deposits 
crystals  of  moist  or  brown  sugar.  The  mother  liquor  is  again 
evaporated,  and  again  allowed  to  cool  and  deposit  another 
crop  of  crystals  ;  the  dark-colored,  uncrystallizable  sugar  is 
termed  molasses,  or  treacle.  The  refining  of  sugar  is  a  pro 
cess  conducted  chiefly  in  England.  The  raw  sugar  is  dis 
solved,  and  again  boiled  with  lime  and  filtered.  The  filtered 
liquor  is  then  decolorized  by  flowing  through  a  thick  bed  of 
animal  charcoal,  and  the  colorless  filtrate  evaporated  down  to 
the  point  of  crystallization,  under  diminished  pressure,  in 
vacuum-pans.  The  object  of  this  is  to  enable  the  syrup  to 
boil  at  a  lower  temperature  than  it  would  do  under  the  ordi- 
nary  pressure,  and  thus  to  prevent  formation  of  uncrystal 
lizable  sugar,  and  to  avoid  the  charring  and  coloring  of  the 
syrup  which  then  takes  place.  The  concentrated  syrup  is 
then  either  allowed  to  crystallize  in  moulds,  giving  loaf  sugar, 
or  the  small  crystals  are  freed  from  adhering  mother  liquor 
by  quick  drying  in  a  hydro-extractor,  or  rapidly  revolving 
sieve.  Much  saving  is  attained  by  the  use  of  the  vacuum- 
pans,  and  if  its  employment  were  universal  in  the  colonies, 
where  the  sugar  is  first  prepared,  the  formation  of  much 
treacle,  or  uncrystallizable  sugar,  would  be  avoided,  and  the 
profit  to  the  planter  proportionately  increased.  A  method  of 
treating  the  cane-juice  has  lately  been  proposed,  which  bids 
fair  to  revolutionize  the  manufacture  of  raw  sugar.  It 
depends  upon  the  fact,  that  by  a  peculiar  plan  of  rapid  eva 
poration,  the  whole  of  the  water  can  be  got  rid  of,  without 
charring  the  sugar,  which  is  thus  obtained  as  a  solid  mass, 
and  all  formation  of  treacle  avoided. 

Sugar  crystallizes  in  monoclinic  prisms,  which  phospho 
resce  when  broken:  its  specific  gravity  is  1*606.  It  is  so 
luble  in  one-third  of  its  weight  of  cold,  and  in  rather  more  of 
hot,  water,  and  is  nearly  insoluble  in  alcohol  and  ether.  Its 
specific  power  of  rotation  is  73°8'  to  the  right.  Sugar  melts 


Elementary  Chemistry.  311 

at  1 60°  to  a  colorless  liquid,  which  solidifies  on  cooling  to  a 
colorless  transparent  mass  (barley- sugar),  and,  on  standing, 
becomes  crystalline  and  opaque.  When  more  strongly 
heated,  water  is  given  off,  and  a  dark  colored  mass,  called 
caramel,  is  left  behind.  When  acted  on  by  nitric  acid,  either 
saccharic  or  oxalic  acid  is  formed,  according  to  the  strength 
of  the  acid  and  the  heat  employed.  Strong  sulphuric  acid 
converts  sugar  into  a  black  mass,  with  evolution  of  sulphuric 
dioxide.  A  mixture  of  these  two  acids  in  the  cold  acts  on 
sugar  to  form  a  nitro-substitution  product,  Ci2Hi8  (NO^Ou, 
an  amorphous  mass,  liable  to  explode  on  percussion.  Solu 
tions  of  sucrose  easily  reduce  the  noble  metals  from  their 
solutions  on  warming,  whilst  cupric  salts  are  only  slowly  de 
composed  in  alkaline  solution  of  sucrose.  Cane-sugar  is  not 
directly  fermentable,  but,  in  presence  of  yeast,  it  takes  up  a 
molecule  of  water  and  forms  a  mixture  of  dextrose  and  levu- 
lose,  both  capable  of  undergoing  fermentation  : — 

Ci2H22On  +  H2O  =  C6Hi2OG  +  CcH12O6. 

Sucrose.  Dextrose.  Levulose. 

By  the  action  of  dilute  sulphuric  acid,  the  same  change 
is  produced ;  and  also  by  long  continued  boiling  of  a 
solution  of  sugar.  Sucrose  combines  with  certain  metal 
lic  oxides  to  form  definite  compounds  ;  thus  we  have 
Ci2H22On  CaO,  whilst  other  metals  replace  some  of  the 
hydrogen  of  the  sugar  ;  thus  lead  forms  a  compound 
having  the  formula  Ci2Hi8Pb2On. 

Lactose,  or  milk  sugar,  occurs  only  in  the  milk  of  mam 
malia,  from  which  it  is  obtained  in  the  crystalline  state  by 
evaporation.  The  crystals,  which  are  rhombic,  contain  an 
atom  of  water  of  crystallization,  given  off  at  140°.  Lactose 
dissolves  in  6  parts  of  cold  and  2  parts  of  boiling  water ;  it 
does  not  possess  nearly  so  sweet  a  taste  as  sucrose,  and  feels 
gritty  in  the  mouth,  and  its  specific  power  of  rotation  is 
+  59°3'.  Lactose  does  not  ferment  itself,  but  when  much 
yeast  is  added,  fermentation  occurs,  after  some  time,  mannite 
being  formed.  In  presence  of  cheese,  &c.,  the  lactic  fer- 


312  Elementary  Chemistry. 

mentation  sets  in.  Dilute  acids  convert  lactose  into  a  pe 
culiar  glucose,  called  galactose,  which  is  directly  fermentable, 
and  yields  mucic  acid  when  treated  with  nitric  acid.  Lactose 
reduces  an  alkaline  copper  solution  in  the  cold,  precipitating 
cuprous  oxide  ;  but  the  quantity  of  this  substance  formed  is 
not  so  great  as  when  the  same  weight  of  glucose  is  employed. 
Lactose,  when  oxidized,  yields  mucic,  saccharic,  tartaric,  and 
oxalic  acids. 

GLUCOSES,  C6Hi2O6.  Dextrose,  or  right-handed  glucose, 
grape-  or  starch-sugar,  is  found  in  many  kinds  of  fruit,  in 
manna  and  honey  mixed  with  levulose,  or  left-handed  glu 
cose.  It  forms  a  normal  constituent  of  blood,  white  of 
egg,  and  exists  in  small  quantity  in  healthy  urine,  whilst 
it  is  excreted  in  large  quantities  in  that  liquid  in  the  disease 
termed  diabetes. 

Dextrose  is  formed  in  many  ways. 

(i.)  By  boiling  starch  or  dextrine  with  diluted  acids. 

(2.)  By  the  action  of  malt  upon  starch  (see  Dextrine). 

(3.)  By  the  action  of  dilute  acids  upon  sucrose  (when  it  is 
formed  together  with  levulose. 

(4.)  By  the  action  of  acids  upon  many  glucosides. 

Dextrose  is  prepared  by  boiling  starch  with  dilute  sulphuric 
acid,  adding  chalk  to  neutralize  the  acid,  and  evaporating  the 
liquid  to  a  syrup  when  the  sugar  crystallizes.  It  may  also 
be  easily  prepared  by  washing  honey  with  dilute  alcohol ;  the 
levulose  being  more  soluble  is  thus  removed.  Dextrose  turns 
the  plane  of  polarization  to  the  right :  its  permanent  rotation- 
power  is  +56°.  It  is  soluble  in  its  own  weight  of  water,  and 
dissolves  easily  in  dilute  alcohol,  and  is  not  nearly  so  sweet 
as  sucrose  ;  the  crystals  contain  one  molecule  of  water, 
which  they  lose  at  60°.  Dextrose  immediately  precipitates 
red  cuprous  oxide  from  alkaline  cupric  solutions  ;  and  the 
quantity  of  dextrose  present  in  a  solution  can  be  ascertained 
by  employing  a  standard  solution  of  alkaline  copper  salt. 
From  silver  salts  the  metal  is  deposited  by  dextrose,  in  the 
form  of  a  mirror.  Nitric  acid  oxidizes  dextrose  to  saccharic 
or  oxalic  acid. 


Elementary  Chemistry.  313 

Levulose,  or  left-handed  glucose.  This  forms  an  incrystal- 
lizable  colorless  syrup  ;  it  is  more  soluble  in  water  and  alcohol 
than  dextrose,  and  is  therefore  sweeter.  Its  action  on  po 
larized  light  changes  remarkably  with  the  temperature  :  thus 
at  a  temperature  of  I4°C.  its  rotatory  power  is  106°,  whereas 
at  90° C.  it  is  reduced  to  53°.  Levulose  reduces  cupric  salts 
like  dextrose  ;  it  is  obtained  by  neutralizing  with  lime  the 
mixture  of  glucoses  obtained  by  the  action  of  sulphuric  acid 
on  sucrose.  The  levulose  lime-compound  is  a  solid,  whilst 
dextrose  forms  a  liquid  substance.  By  decomposing  this 
lime-compound  with  oxalic  acid  pure  levulose  is  obtained. 

The  acids  having  the  composition  C6Hi0  O8  (inucic  and 
saccharic)  obtained  by  the  action  of  dilute  nitric  acid  on  the 
different  sugars,  must  be  regarded  as  products  of  oxidation 
of  mannite,  the  hexatomic  alcohol  :  levulose  yields  mannite 
when  acted  on  by  nascent  hydrogen,  and  hence  stands  to  this 
substance  as  aldehyde  to  alcohol. 


Mannite,  C<!  J*8  I  Oe 

rie  \ 


CeH6 


H6  >  n  Ce  He  O  )  n  Ce  H4  O2  )  n 

Hf    ^6.  TT        f    V^fi                                             TT        f    V^8. 

6  )  -He  )                                 rle  ) 

Levulose.  Mannitic  Acid.  Mucic  and  Saccharic  Acids. 


Alcohol,  C2  Jt5  [  O. 


C8  H3  )  0  C2  H3  O  )  n 

H    f  u  H  f  u' 

Aldehyde.  Acetic  Acid. 

FERMENTATION.  This  name  has  been  given  to  a  peculiar 
and  interesting  class  of  decompositions,  which  have  long 
been  known,  but  differ  altogether  from  the  ordinary  chemical 
actions.  Many  organic  bodies  are  capable  of  undergoing 
fermentation  in  presence  of  certain  complicated  substances 
termed  ferments,  giving  rise  to  several  products  differing  ac 
cording  to  the  nature  of  the  fermented  body  and  the  ferment. 
Careful  investigation  has  shown  that  the  process  of  fermenta 
tion  entirely  depends  upon  the  presence  and  growth  of  cer- 

14 


314  Elementary  Chemistry. 

tain  living  organisms  forming  the  ferment.  Different  kinds 
of  ferments  give  rise  to  different  products.  Thus  we  have 
one  ferment  (yeast)  which  effects  the  alcoholic  fermentation, 
another  which  sets  up  the  lactic  fermentation,  a  third  produ 
cing  the  acetous  fermentation,  &c.  Most  of  these  ferments 
are  vegetable  growths  of  a  low  kind,  but  one  at  least,  viz., 
that  causing  the  butyric  fermentation,  is  an  animal ;  and  this, 
strange  to  say,  cannot  live  in  contact  with  free  oxygen,  but 
flourishes  in  an  atmosphere  of  hydrogen.  In  order  that  the 
ferment  should  grow,  it  must  be  supplied  with  proper  food, 
especially  with  ammoniacal  salts  and  alkaline  phosphates  ; 
these  are  contained  in  the  albuminous  matter  generally 
present  in  the  liquid  about  to  be  fermented.  In  order  that 
the  fermentation  should  go  on  well,  the  temperature  should 
be  from  20°  to  40°  ;  at  much  higher,  as  at  much  lower  tem 
peratures,  the  vitality  of  the  ferment  is  destroyed. 

In  many  cases,  spontaneous  fermentation  sets  in  without 
the  apparent  addition  of  any  ferment :  thus  wine,  beer,  milk, 
urine,  &c.,  when  allowed  simply  to  stand  exposed  to  the  air, 
become  sour  or  otherwise  decompose.  These  changes  are, 
however,  not  effected  without  the  presence  of  vegetable  or 
animal  life,  and  are  true  fermentations  ;  the  sporules,  or  seeds 
of  these  living  bodies,  always  float  about  in  the  air,  and  on 
dropping  into  the  liquid  begin  to  propagate  themselves,  and 
in  the  act  of  growing -evolve  the  products  of  the  fermentation. 
If  the  above  liquids  be  left  only  in  contact  with  air  which  has 
been  passed  through  a  red-hot  platinum  tube,  and  thus  the 
living  sporules  destroyed ;  or  if  the  air  be  simply  filtered  by 
passing  through  cotton  wool,  and  the  sporules  prevented  from 
coming  into  the  liquid,  it  is  found  that  these  fermentable 
liquids  may  be  preserved  for  any  length  of  time  without  un 
dergoing  the  slightest  change. 

The  following  are  the  five  principal  forms  of  fermenta^ 
tion  : 

1.  The  alcoholic   fermentation,  producing  chiefly  alcohol 
and  carbonic  acid. 

2.  The  acetous  fermentation,  producing  acetic  acid. 


Elementary  Chemistry.  315 

3.  The  lactic  fermentation,  yielding  chiefly  lactic  acid. 

4.  The  butyric  fermentation,  yielding  chiefly  butyric  acid. 

5.  The  mucous  fermentation,  giving  rise  to  gum  and  man- 
nite. 

Alcoholic  Fermentation.  The  glucoses  are  able,  when  dis 
solved  in  presence  of  yeast,  to  undergo  fermentation,  evolv 
ing  mainly  alcohol  and  carbonic  acid, — 

C6H1206  =  2  C2H6O  +  2  CO2. 

About  6  per  cent  of  the  glucose  undergoes  a  different 
change,  part  being  used  as  nourishment  for  the  yeast,  and 
another  part  forming  glycerine  and  succinic  acid.  From  100 
parts  of  glucose  about  3-5  parts  of  glycerine  are  produced, 
and  o'6  to  07  of  succinic  acid,  whilst  1-2  to  1-5  parts  of  cel 
lulose  and  fatty  matter  are  formed  by  the  growth  of  the 
yeast.  The  alcoholic  fermentation  occurs  best  at  a  tempera 
ture  of  between  25°  and  30°. 


LESSON  XXXVIII. 

ir-     *-*> 

AMYLACEOUS  BODIES  AND  GUMS.     j£>  , 

Dextrine,  C6  HioO5.  This  substance,  called  British  Gum, 
is  prepared  by  heating  starch  to  about  150°  ;  if  a  small  quan 
tity  of  nitric  or  hydrochloric  acid  is  added  to  the  starch,  the 
transformation  takes  place  much  more  rapidly.  Dextrine  is 
also  formed  together  with  dextrose  by  the  action  of  malt 
extract  upon  starch.  It  deviates  the  plane  of  polarization 
strongly  to  the  right,  its  rotatory  power  being  4- 138°7'.  Dex 
trine  is  very  soluble  in  water  and  insoluble  in  alcohol,  and 
on  boiling  with  dilute  acids  dextrine  is  converted  into  dex 
trose. 

Gum  Arabic.     The  natural  exudation  from  several  species 


316  Elementary  Chemistry. 

of  acacias  ;  it  consists  chiefly  of  the  potassium  and  calcium 
salts  of  arabic  acid,  Ci2  H™  Oio. 

Inulin.  A  substance  contained  in  the  roots  of  many 
plants  ;  it  is  intermediate  between  gums  and  starch  ;  it  yields 
levulose  when  boiled  with  dilute  acids. 

Glycogcn,  or  Animal  Starch,  is  an  insoluble  powder 
formed  in  the  liver  and  placenta ;  it  is  easily  converted  into 
glucose. 

Starch,  C6  Hio  O5  (or  some  multiple  of  these  numbers). 
This  important  substance  exists  most  widely  diffused  through 
out  the  vegetable  world.  It  consists  of  a  white  powder 
composed  of  granules  which  have  a  distinctly  organized 
structure,  and  are  of  various  sizes.  The  following  are  the 
diameters  of  the  granules  of  some  of  the  most  important 
varieties  of  starch  : 

Potato    o'iSf  mm.        Wheat    .     .  0*050  mm.        Millet    .  o'oiomm. 
Sago    .  0*070    "  Indian  corn  0*030    "  Beetroot  0^004    " 

Starch  granules  are  insoluble  in  cold  water,  alcohol,  and 
ether,  but  when  they  are  heated  with  water  to  between  70° 
and  72°  they  swell  up  and  split  open,  forming  a  thick  mass 
called  Starch  Paste.  If  this  paste  be  boiled  with  a  larger 
quantity  of  water,  the  particles  of  starch  become  so  finely 
divided  that  they  pass  through  a  filter,  and  if  boiled  for  a 
length  of  time,  the  solution  becomes  clear,  and  the  starch  is 
rendered  soluble  ;  and  from  this  solution  alcohol  precipitates 
a  white  amorphous  powder  of  soluble  starch.  When  heated  to 
160°  starch  is  converted  into  dextrine.  Starch,  in  its  insoluble 
and  soluble  modifications,  forms  with  free  iodine  a  deep  blue 
compound,  the  color  of  which  is  destroyed  a  little  below  100°, 
but  appears  again  on  cooling.  This  color  is  characteristic 
of  starch,  and  is  not  produced  with  dextrine  or  the  other 
isomers  of  starch.  When  the  soluble  azotized  matter  con 
tained  in  malt,  called  diastase,  acts  upon  starch,  it  forms 
dextrine  and  dextrose  ;  and  by  a  longer  action  the  dextrine  is 
also  converted  into  dextrose. 


Elementary  Chemistry.  317 

3  (C«  H10  O6)+  H2  O  =  da  H20  do  +  C6  Hia  O6, 

Dextrine.  Dextrose. 

The  action  of  dilute  sulphuric  acid  upon  starch  is  similar 
to  that  of  diastase.  Strong  sulphuric  acid  in  the  cold  dis 
solves  starch,  forming  a  compound  acid  ;  nitric  acid  also  dis 
solves  starch,  and  on  adding  water  to  the  solution  a  white 
substance  called  xyloidine  is  precipitated  ;  this  is  a  substitu 
tion  product,  being  starch  in  which  one  atom  of  hydrogen  is 
replaced  by  N  O2,  thus  :  C12  H19  (NO2)  O10. 

Cellulose,  C6  Hio  06.  This  is  the  colorless  material  of  the 
woody  fibre  of  young  plants  ;  it  may  be  obtained  in  the  pure 
state  from  cotton  or  linen  fibre  by  boiling  out  the  impurities 
with  alkali,  alcohol,  ether,  &c.  Cellulose  is  a  white  substance 
insoluble  in  water,  alcohol,  or  ether,  but  dissolving  in  an  am- 
moniacal  solution  of  cupric  oxide.  By  the  action  of  strong 
sulphuric  acid,  cellulose  is  converted  either  into  an  insoluble 
substance  which  colors  blue  with  iodine,  or  into  a  soluble  body 
like  dextrine  ;  if  this  acid  solution  be  diluted  with  water  and 
boiled,  dextrose  is  formed  by  fixation  of  one  molecule  of 
water.  A  useful  substance  is  obtained  under  the  name  of 
parchment  paper,  by  dipping  sheets  of  paper  into  strong  sul 
phuric  acid. 

Gun  Cotton.  The  action  of  strong  nitric  acid  upon  cellu 
lose  is  interesting ;  if  cotton  wool  be  thrown  in  small  por 
tions  at  a  time  into  a  mixture  of  equal  volumes  of  strong 
sulphuric  and  nitric  acids,  it  does  not  undergo  any  apparent 
change,  but  on  drying  it  is  found  to  be  very  inflammable.  It 
is  a  substitution  product,  being  cellulose  in  which  two  or 
more  atoms  of  hydrogen  are  replaced  by  (N  O2)  thus  : 
C8  H8(N  O2)2O5.  By  the  action  of  ferrous  chloride  nitric 
oxide  is  evolved  and  cellulose  again  formed.  The  use  of 
gun-cotton  as  a  substitute  for  gunpowder  has  been  proposed, 
as  it  offers  many  advantages  : — • 

(i)  The  explosive  force  of  gun-cotton  is,  weight  for  weight, 
greater  than  that  of  gunpowder.  (2)  The  products  of  com 
bustion  of  gun-cotton,  being  chiefly  carbonic  acid  and  nitro- 


318  Elementary  Chemistry. 

gen,  are  not  so  apt  to  foul  the  gun.  (3)  When  moistened  it 
becomes  inexplosive,  and  only  requires  drying  to  render  it 
again  explosive. 

The  reasons  which  render  the  general  adoption  of  this  sub 
stance  doubtful  are  (i)  its  liability  to  explode  on  percussion  ; 
(2)  the  possibility  of  its  spontaneous  decomposition  when 
kept  for  a  length  of  time. 

Gun-cotton,  or  certain  forms  of  this  substance,  dissolves 
readily  in  a  mixture  of  ether  and  alcohol,  and  yields  a  solu 
tion  which  is  termed  Collodion,  and  is  largely  used  for  the 
purpose  of  forming  a  thin  coating  on  glass  to  receive  silver 
salts,  upon  which  the  photographic  image  is  formed. 


GROUP  OF  GLUCOSIDES. 

The  numerous  substances  constituting  this  class  occur  in 
the  bodies  of  many  plants,  and  yield  a  glucose  on  decomposi 
tion,  together  with  other  bodies  ;  they  may  be  considered  as 
kinds  of  compound  ethers  of  glucose.  The  most  important 
are  amygdaline,  salicine,  and  tannine. 

Amygdaline,  C20  H27  NOn  +  3  H2  O.  Found  in  bitter  al 
monds,  and  obtained  by  dissolving  out  by  alcohol,  and  preci 
pitating  the  amygdaline  with  ether ;  it  forms  small  white 
crystals  which  are  soluble  in  water.  The  most  remarkable 
decomposition  which  amygdaline  undergoes  is  that  which  is 
brought  about  in  the  bruised  almond  by  the  presence  of  an 
albuminous  substance  called  Synaptase,  by  which  bitter  al 
mond  oil,  hydrocyanic  acid,  and  glucose,  are  produced  : — 

Cao  H27  NOn  +  2Ha  O  =  C7  H6  O  +  H  CN  +  2C6  H19  O6. 

Amygdaline.  Hydride  of        Hydrocyanic        Glucose. 

Benzoyl.  Acid. 

Salicine,  Ci3  Hi8  O7,  contained  in  the  pith  of  the  willow 
and  poplar,  and  also  found  in  the  castoreum  contained  in  a 
gland  of  the  beaver.  Salicine  crystallizes  in  bright  white 
needles  ;  it  is  soluble  in  water  and  alcohol,  but  insoluble  in 


Elementary  Chemistry.  319 

ether,  and  its  solution  possesses  a  strongly  bitter  taste.     In 
presence  of  certain  ferments  it  is  decomposed  as  follows  : 

C13H18O7  +  H2O  =  C7H8O2  +  C6H1206. 

Salicine.  Saligenine.  Glucose. 

Tannine,  or  Tannic  Acid,  C27  H22  Oi7.  This  substance  is 
contained  widely  diffused  in  certain  parts  of  plants  ;  it  is 
distinguished  by  forming  an  insoluble  compound  with  gelatin, 
and  by  producing  a  black  color  (ink)  with  ferric  compounds. 
Tannic  acid  occurs  in  largest  quantities  in  gall-nuts  (an  ex 
crescence  formed  on  the  oak  by  an  insect)  ;  it  is  extracted  by 
aqueous  ether  from  the  powdered  gall-nut.  Tannine  thus  pre 
pared  is  an  uncrystallizable  mass,  soluble  in  water  and  alco 
hol,  but  insoluble  in  pure  ether.  Tannine  forms  glucose  and 
gallic  acid  when  it  is  exposed  to  the  air,  or  when  treated  by 
dilute  acids. 

C27  H22  On  +  4  H2  O  =  3  CT  H6  O5  +  C8  Hi2  O6 

Tannine.  Gallic  Acid.  Glucose. 

Tannine  heated  to  215°  yields  pyrogallic  acid. 


LESSON  XXXIX. 

THE  GROUP  OF  AROMATIC  COMPOUNDS. 

It  has  already  been  stated  that  in  these  bodies  the  carbon 
atoms  are  more  closely  combined  together  than  is  the  case  in 
the  foregoing  group,  or,  in  other  words,  that  the  aromatic 
hydro-carbons  contain  relatively  less  hydrogen  than  those 
which  we  have  hitherto  studied.  Another  peculiarity  of  these 
substances  is,  that  they  contain  at  least  6  atoms  of  carbon, 
and  that  the  more  complicated  compounds  split  up  into  those 
containing  6  carbon  atoms.  It  appears  in  fact  that  all  the 
aromatic  bodies  contain  a  group  of  6  carbon  atoms,  in  which 
18  of  the  combining  powers  of  the  carbon  are  taken  up  by 


320  Elementary  Chemistry. 

union  of  carbon  with  carbon  (p.  232),  whilst  6  remain  open  to 
saturation. 

The  simplest  combination  amongst  the  aromatic  series  is 
that  of  benzol,  Ca  H6,  and  from  this  body  a  large  number  of 
other  substances  can  be  derived  by  substitution  of  one  or 
more  atoms  of  hydrogen  by  more  or  less  complicated  mole 
cules.  Thus,  for  instance,  we  are  acquainted  with  four  hydro 
carbons  homologous  with  benzol  but  differing  by  C  H2  ;  these 
substances  are  in  fact  benzol,  in  which  i,  2,  or  3  atoms  of 
hydrogen  have  been  replaced  by  methyl,  C  H3.  We  thus 
have  : 

Boiling  Point 

(1)  Benzol    .     .     .     .     C6  H6  #2° 

(2)  Toluol,  or      )      r  w         r  TT    ru  ,  0 
Methyl-Benzol  f      ClH"  or  C°H'(CH°) 

(3)  Xylol,  or  Di-      >      r  „          r  „     j  CH3 
methyl  Benzol   j      C8H10,  or  C«H4  |  CH3  139 

(4)  Cumol,  or  Tri-    )      r  „  r  „     \  p"3  ™0 

C9Hl2  O1  CeH3 


,  -          r  „  r  „ 

methyl  Benzol  f      C9Hl2'  O1  CeH 

Each  of  these  methylated  benzols  yields  an  important 
series  of  derivatives,  corresponding  to  those  obtained  from 
benzol.  Thus  in  each,  one  or  more  atoms  of  hydrogen  can 
be  replaced  (i)  by  chlorine,  giving  chlorine  substitution  pro 
ducts  ;  (2)  by  the  monad  NO2  yielding  nitro-substitution  pro 
ducts  ;  (3)  by  the  monad  N  H2  yielding  amido-compounds  ; 
or  (4)  by  the  monad  HO  yielding  a  peculiar  set  of  alcohol-like 
bodies,  termed  Phenols,  as  well  as  a  series  of  true  alcohols, 
isomeric  with  the  phenols.  The  following  table  gives  the 
names  and  formulae  of  some  of  the  derivatives  of  benzol,  and 
methyl-benzol,  or  toluol  :  — 

Benzol    .....     C6  H« 
Monochlor-benzol     .     C6  H5  Cl 
Nitro-benzol    .    .     .     C6  H6  (NO2) 


Elementary  Chemistry.       v  /  /    321 

\  >  /• 

AmidA0;^lZOl'°^    •     C6H5(NH2) 

:?//;^/?,  ** 
</#>.   '  - 


e      5          2  , 

Aniline  >  / 

Phenol,    or    Car- 


Toluol CT  H8,  or  C6  H5  (CH.) 

Monochlor-toluol  .     .     C7  H7  Cl,  or  C6  H4  Cl  (CHa)         /'  , 
Nitro-toluol       .     .     .     C7  H7  NO2,  or  C6  H4  (NOa)  (CH3)  ' 

Amido-tpjuol,  or  )  ^    ^    ^        ^    ^    (NH2)  (CH3) 

Toluidme       ) 

Cressol C7  H8  O,  or  C6  H4  (HO)  (CH») 

A  series  of  bodies,  isomeric  with  these  toluol*compounds, 
exists,  in  which  the  substitution  takes  place  with  the  hydro 
gen  of  the  methyl.  This  is  termed  the  Benzyl  series. 

Toluol.  Benzyl  Chloride. 

C7  H8,  or  C6  H5  (CHS)         C7  H7  Cl,  or  C6  H6  (CH2  Cl) 

Benzylamine. 

C7  H7  )  C6  H5  (CHa)  ) 

H   V.N,  or  H     VN. 

H  3  H     ) 

Benzyl  Alcohol. 

or  ^   TT      [•  O. 

By  oxidation  benzyl  alcohol  yields  an  aldehyde,  C7H6  O,  oil 
of  bitter  almonds,  and  an  acid,  C7  H8  O2,  benzoic  acid,  both 
derived  from  this  alcohol,  as  ethyl  aldehyde  and  acetic  acid 
are  derived  from  ethyl  alcohol. 

The  di-  and  tri-methyl  benzols  also  furnish  similar  double 
series  of  isomeric  derivatives.  In  like  manner  all  the  higher 
alcohol  radicals,  ethyl,  propyl,  butyl,  &c.,  can  be  substituted 
for  one  or  more  atoms  of  hydrogen  in  benzol,  and  thus  an 
almost  unlimited  number  of  isomeric  bodies  may  be  pre 
pared  ;  thus  ethyl  benzol,  C8  H6  (C2H6),  is  isomeric,  but  not 

f  C7-T 
identical  with  di-methyl  benzol  or  xylol,  C8  H*    -j  ^  jj3' 

14* 


322  Elementary  Chemistry. 

Benzol,  Ce  H8.  Found  in  the  light  oils  obtained  by  the 
destructive  distillation  of  coal  ;  it  is  a  colorless  liquid,  refract 
ing  light  powerfully,  boiling  at  82°,  and  freezing  at  — 4°'5.  It 
is  also  obtained  by  distilling  benzoic  acid  with  slacked  lime. 
Benzol  is  attacked  by  chlorine,  and  several  chlorides  formed  ; 
•when  treated  with  nitric  acid,  an  interesting  substance  called 
nitro-benzol,  Ce  H6  (NO?),  is  produced,  a  substitution  pro 
duct  in  which  one  of  hydrogen  of  benzol  is  replaced  by  N  Oa  ; 
and  we  also  know  a  solid  substance  called  di-nitro-benzol, 
C6  H4  2  (NOa).  In  contact  with  reducing  agents,  nitro-ben 
zol  undergoes  the  following  important  reduction  to  aniline,  in 
which  the  monad  group  (NOa)  is  replaced  by  the  monad 
(N  Ha),  thu»: 

Ce  He  (NOa)  +  3  Ha  =   Ce  H5  (NHa)  +  2  Ha  O. 

Nitro-benzol.  Aniline. 

Phenol,  or  Carbolic  Acid,  C0  H5  (HO).  This  is  a  white 
solid  crystalline  body,  fusing  at  35°,  and  boiling  at  188°,  found 
in  the  heavy  coal-oils.  It  dissolves  in  the  alkalies,  forming  a 
phenate,  but  it  does  not  possess  an  acid  reaction.  The  most 
important  property  of  this  body  is  its  powerful  antiseptic 
qualities,  and  it  is  much  used  as  a  disinfectant,  both  alone 
and  when  combined  with  lime. 

Monochlor  Benzol,  C8  H8  Cl,  is  formed  by  the  direct  action 
of  chlorine  on  benzol,  or  when  phosphorus  penta-chloride 
acts  upon  phenol. 

Picric  Acid,  C6  H3  (NO2)s  O.  When  phenol  is  acted  upon 
by  nitric  acid,  i,  2,  or  3  atoms  of  hydrogen  may  be  substi 
tuted  by  NOa.  Tri-nitro  carbolic  acid,  or  picric  acid,  is  a 
bright  yellow  crystalline  body,  very  soluble  in  water  ;  it  is 
obtained  by  the  action  of  nitric  acid  upon  many  other  sub 
stances  besides  carbolic  acid  and  its  derivatives.  Picric  acid 
is  employed  in  the  arts  as  a  yellow  dye  for  silk  and  woollen 
goods. 

Aniline,  or  Amido-benzol,  C8  H6  (NHa).  This  important 
body  is  benzol,  in  which  one  atom  of  hydrogen  is  replaced  by 
the  monad  group  (NH2),  and  it  is,  therefore,  properly  called 


Elementary  Chemistry.  323 

Amido-benzol.  The  mode  of  preparing  aniline  from  benzol 
has  just  been  described,  the  reduction  of  nitro-benzol  being 
generally  effected  by  a  mixture  of  iron  filings  and  acetic  acid. 
It  may  also  be  obtained  by  the  action  of  potash  on  isatine 
(P-  323). 

C8  H5  NO2  +  4  (KHO)  =  C6  H7  N  +  2  (K2  CO3)  +  Ha. 

Isatine.  Aniline.  Potassium  Carbonate. 

It  is  also  found  amongst  the  products  of  the  destructive 
distillation  of  coal. 

Aniline  is  a  colorless  liquid,  possessing  a  peculiar  smell  ; 
its  specific  gravity  at  o°  is  1*036,  and  it  boils  at  185°.  It  is 
nearly  insoluble  in  water,  but  dissolves  in  alcohol  and  ether  ; 
it  unites  with  acids  to  form  definite  salts,  but  it  does  not  turn 
red  litmus  paper  blue.  Crude  aniline  is  manufactured  now  on 
a  very  large  scale  for  the  preparation  of  the  so-called  aniline 
colors,  so  generally  used  in  calico-printing,  and  woollen  and 
silk  dyeing.  The  smallest  trace  of  aniline  may  be  easily 
detected  by  adding  to  an  aqueous  aniline  solution  an  aqueous 
solution  of  an  alkaline  hypochlorite,  when  a  splendid  red  col 
oration  is  formed :  this  is  prepared  in  quantity  by  adding  to 
aniline  sulphate  a  dilute  solution  of  potassium  bichromate. 
This  substance  forms  one  of  the  important  aniline  colors,  and 
is  called  mauve;  it  contains  a  base  of  complicated  constitu 
tion,  termed  mauveine.  The  color  mauve  can  be  prepared  by 
many  other  methods  ;  the  best  of  these  is  by  heating  aniline 
with  a  double  chloride  of  sodium  and  copper.  The  other 
coloring  matters  derived  from  aniline  are  noticed  on  the  next 
page.  Ariline  gives  rise  to  a  very  large  number  of  deriv 
atives  ;  thus  we  have  a  series  of  compounds  in  which  one  or 
more  atoms  of  hydrogen  are  replaced  by  ethyl  and  other 
radicals.  We  are  also  acquainted  with  di-amido  benzol,  thus  : 

C6  H5  (NH2)  C6  H4  2  (NHa) 

Aniline  or  Amido-benzoL  Di-amido-benzol. 

C6  H5) 

Aniline  has  been  called  Phenylamine,       H    >  N,  but  it  can- 

H    i 


324  Elementary  Chemistry. 

not  be  prepared  like  an  amine  ;  and  it  is  therefore  better  to 
regard  it  as  an  amido  substitution  product. 

Benzylic,  or  Tohtic  Series.  Tohwl,  or  Methyl-benzol. 
C7  H8  =  C6  H5  (CH3).  This  hydrocarbon  occurs  likewise 
in  the  coal-oils,  and  it  boils  at  m° ;  it  is  also  formed  by  the 
distillation  of  toluic  acid  with  excess  of  lime.  It  can  be  pre 
pared  synthetically  from  benzol  by  replacing  one  atom  of  hy 
drogen  by  methyl  (p.  320).  By  the  action  of  oxidizingagents 
it  is  converted  into  benzoic  acid,  thus  :  C7  H8  +  Oa  =  C7  H8 
02  +  H2  O. 

Nitro-toluol,  C7  H7  (NO-),  is  obtained  by  the  action  of 
nitric  acid  upon  toluol,  and  by  reduction  a  basic  substance  is 
obtained  analogous  to  aniline,  and  called  amido-toluol,  or 
Toluidine,  C7  H9  N  or  C6  H5  (NH,)  (CH3).  This  is  a  solid 
substance,  which  exists  always  in  commercial  aniline,  and  in 
fact  is  a  necessary  ingredient  for  the  purpose  of  the  manu 
facture  of  the  red  and  violet  aniline  colors.  Toluidine  fuses 
at  40°,  and  boils  at  198°.  Toluidine  is  isomeric  with  benzyl- 
amine. 

Cressol,  C7  H7  (HO),  a  crystallizable  solid,  homologous 
with  phenol,  contained  in  the  crude  carbolic  acid  ;  it  boils  at 
203°. 

Rosaniline,  Cso  Hi9  N3.  The  compounds  of  this  substance 
form  the  splendid  red-aniline  color,  known  as  magenta.  The 
color  may  be  obtained  in  various  ways,  from  crude  aniline  ; 
the  best  process  consists  in  heating  this  crude  substance  and 
arsenic  acid  together  to  a  temperature  of  from  120°  to  140° ; 
the  quantities  taken  being  12  parts  of  dry  arsenic  acid  of  com 
merce  (containing  13-5  per  cent,  of  water)  to  10  parts  of 
aniline.  The  color  cannot,  however,  be  prepared  at  all  from 
pure  aniline ;  the  presence  of  toluidine  is  necessary  for  its 
formation.  It  is  a  singular  fact,  that  the  pure  base,  rosani- 
line,  is  a  colorless  substance,  and  that  it  is  only  in  its  salts 
that  its  magnificent  coloring  powers  become  visible.  The 
crystals  exhibit  by  reflected  light  the  metallic  green  color 
of  beetles'  wings,  but  are  of  a  deep  red  color  when  viewed 
by  transmitted  light ;  the}7  are  soluble  in  alcohol,  yielding 


Elementary  Chemistry.  325 

splendid  red  solutions.  By  the  action  of  nascent  hydrogen 
on  rosaniline,  a  new  base  is  formed  which  forms  colorless 
salts  ;  to  this  the  name  of  Leucaniline  has  been  given.  It 
contains  2  atoms  more  hydrogen  than  rosaniline,  these  two 
bodies  standing  in  the  same  relation  as  blue  and  white  indigo 
(p.  328). 

An  Aniline  bine  \s  obtained  by  the  replacement  of  3  atoms 
of  hydrogen  in  rosaniline  by  phenyl,  C8  H5,  whilst  a  violet  is 
obtained  by  substituting  3  of  methyl,  ethyl,  or  any  of  the  al 
cohol  radicals. 

/-«       TT        \ 

Benzyl  Alcohol,  ^  (  O,  obtained  by  the  action  of  al 
coholic  potash,  or  nascent  hydrogen,  on  oil  of  bitter  almonds 
(which  is  the  aldehyde  of  the  series).  It  is  an  oily  colorless 
liquid,  boiling  at  207°.  Oxidizing  agents  convened  first  into 
the  aldehyde,  C7  H8  O,  and  lastly  into  the  acid  of  the  series, 
C7  H6  O2,  benzoic  acid. 

Benzoic  Aldehyde.'  Oil  of  bitter  almonds,  C?  Hfi  ^  (.  .    This 

oil  does  not  exist  already  formed  in  bitter  almonds,  but  is  the 
result  of  a  decomposition  of  the  amygdaline  contained  in  the 
almond  (p.  318). 

It -can  likewise  be  obtained  by  distilling  a  benzoate  and  a 
formate — in  this  respect  resembling  the  aldehyde  of  the  alco 
hol  group ;  it  also  forms  a  crystalline  compound  with  sodium- 
hydric-sulphite.  Bitter  almond  oil  is  a  colorless  strongly- 
smelling  liquid,  boiling  at  180°  ;  the  commercial  substance 
(used  in  cookery)  is  very  poisonous,  as  it  invariably  contains 
an  admixture  of  hydrocyanic  acid.  On  exposure  to  air  or 
oxygen,  or  when  acted  upon  by  oxidizing  agents,  it  is  con 
verted  into  benzoic  acid.  Benzoic  aldehyde  may  be  regarded 
as  toluol  or  methyl  benzol,  in  which  two  atoms  of  hydrogen 
of  the  methyl  are  replaced  by  one  atom  of  oxygen,  C6  H5 
(C  H  O) ;  whilst  Benzoyl  Chloride,  C7  H5  O  Cl,  is  the  last  sub 
stance  in  which  the  one  remaining  atom  of  hydrogen  in  the 
methyl  is  replaced  by  chlorine.  The  vapor  of  bitter  almond 
oil  decomposes  into  benzol  and  carbonic  oxide  when  passed 


326  Elementary  Chemistry. 

through  a  red-hot  tube  ;  and  benzoyl  chloride  is  formed  by 
the  direct  action  of  chlor-carbonyl  on  benzol,  the  monad 
group  (C  O  Cl)  changing  places  with  one  atom  of  hydrogen, 
thus  : 

CO  Cla     +     C6  H6  =  C6  H5  (C  O  Cl)  +  H  Cl. 

Chlor-carbonyl.  Benzol.  Benzoyl  Chloride. 

Ben-zoyl  chloride  can  also  be  formed  by  the  action  of  phos 
phorus  pentachloride  upon  benzoic  acid  ;  it  is  a  colorless  li 
quid,  boiling  at  199°. 

Benzoic  Acid,     7     5       t  O.     Found  in  many  resins,  espe 


cially  in  gum  benzoin  ;  it  also  occurs  in  the  urine  of  cows, 
and  in  the  putrefied  urine  of  man  and  other  animals  ;  it  can 
be  obtained  by  the  oxidation  of  benzyl  alcohol  and  bitter  al 
mond  oil.  Benzoic  acid  may  be  easily  prepared  by  heating 
gum  benzoin,  when  the  acid  sublimes  in  pearly  white  plates  ; 
it  fuses  at  121°  and  boils  at  250°.  Benzoic  acid  forms  a  series 
of  salts,  most  of  which  are  soluble  ;  the  ferric  benzoate  falls 
as  an  insoluble  red  precipitate  when  sodium  benzoate  is  added 
to  ferric  chloride. 

Benzoic  Peroxide,  ^  jj|  Q]  Ot<  A  well-crystallized  sub 
stance,  obtained  by  the  action  of  barium  peroxide  on  benzoyl 
chloride  ;  it  explodes  when  heated,  and  resembles  acetyl  per 
oxide  (p.  277). 

Benzoic  Benzoate,    or   Benzoic  Anhydride,    ^    jj5  Q  !•  O. 

obtained  by  acting  upon  potassium  benzoate  with  benzoyl 
chloride,  thus  : 

CT  HB  O  \  f^.     ,    /-*    "u    r»  r*i         ^-7  ^5  O 
K  [  °   +  G  HB  °         =  C7  H5  O 

It  is  a  solid  substance,  fusing  at  24°,  and  boiling  at  about 
310°;  it  is  soluble  in  alcohol  and  ether,  and  several  mixed 
anhydrides  are  also  known  —  thus  we  have  acetyl  ben- 


Elementary  Chemistry.  327 


Berisylamine.       H   >-  N  ;  a  colorless  liquid,  isomeric  with 
H  ) 

toluidine,  boiling  at  182°,  obtained  by  the  action  of  ammonia 
upon  benzyl  chloride.  It  is  a  true  amine,  and  gives  rise  to 
corresponding  secondary  and  tertiary  amines. 

Hippuric  Acid,  C9  H9  N  O3,  is  contained  in  the  urine  of 
horses  and  herbivorous  animals.  It  can  also  be  artificially 
prepared  from  zinc  glycocine  and  benzoyl  chloride ;  it  is  in 
fact  glycocine,  in  which  one  atom  of  hydrogen  is  replaced  by 
the  radical  C7  H5  O  of  benzoic  acid,  thus  : 

C2  H3  (NHa)  Oi.      C2  H2  (C7  H5  O)  (NH2  O,. 

Glycocine.  Glycocine-Benzoic  Acid,  or  Hippuric  Acid. 

Benzoic  acid  is  converted  by  passing  through  the  animal 
body  into  hippuric  acid. 

SALICYLIC  GROUP.  This  group  contains  the  dyad  radi 
cals,  C7  H6,  or  C7  H4  O.  Salicylic  acid  stands  to  benzoic  as 
glycolic  to  acetic,  thus  : 

IT        H 

C3  H3  O  )  ^  C2  H2  O 

H 

Acetic.  Glycolic. 

H 

C7  H60 
H 

Benzoic. 

And  as  glycolic  acid  is  obtained  from  monochloracetic  acid 
by  the  action  of  potash,  so  salicylic  acid  can  be  prepared  from 
monochlor-benzoic  acid.  A  glycol  of  this  series  called 
Saligenine  also  e*5sts,  from  which  the  acid  is  obtained  by 
oxidation.  Salicylic  acid  is  formed  as  a  methyl  compound  in 
the  essential  oil  of  Gaultheria  procumbens.  For  a  descrip- 


328  Elementary  Chemistry. 

tion  of  the  remaining  aromatic  compounds  a  larger  work  must 
be  consulted. 

INDIGO.  This  substance  is  the  blue  coloring  matter  de 
rived  from  several  species  of  Indigofera.  The  leaves  are 
macerated  in  water,  when  they  undergo  oxidation,  forming  a 
yellow  substance  which,  on  exposure  to  air,  deposits  indigo  in 
the  form  of  a  dark  blue  powder.  This,  when  evaporated  to 
dryness  and  cut  into  small  cakes,  constitutes  the  indigo  of 
commerce.  The  pure  coloring  matter  termed  Indigotine  is 
obtained  from  commercial  indigo  in  crystals  by  sublimation  ; 
its  composition  is  C»  H3  NO.  Indigo  is  insoluble  in  water 
and  in  cold  alcohol  and  ether  ;  strong,  or  fuming  sulphuric 
acid,  dissolves  indigo,  forming  a  deep  blue  solution.  Indigo 
occurs  sometimes  in  healthy  urine  in  small  quantities.  When 
indigo  is  exposed  in  contact  with  alkalies  to  reducing  agents 
it  passes  into  a  soluble  and  colorless  substance  by  absorption 
of  hydrogen.  The  substance  thus  produced  is  called  white 
indigo j  its  formula  is  C8  H6  N  O.  This  property  is  largely 
employed  in  indigo  dyeing.  An  indigo-vat  being  prepared, 
containing  i  part  of  indigo,  2  parts  of  ferrous  sulphate,  and  3 
parts  of  slaked  lime  to  about  200  parts  of  water,  these  are 
allowed  to  stand  for  some  time  in  a  closed  vessel.  The  cloth 
is  then  dipped  into  the  liquid,  and  on  exposure  to  air  becomes 
permanently  dyed  by  the  deposition  of  insoluble  blue  indigo 
in  the  fibre  of  the  tissue. 

Isatine,  C8  H6  NOa.  By  the  careful  oxidation  of  indigo 
this  substance  is  formed  ;  it  crystallizes  in  large  deep  yellow 
crystals.  By  the  action  of  potash  it  is  converted  into  aniline. 

C8  H,  N  Oa   +   4  K  H  O  =  C,  HT  N  +   2  (Ka  C  Oa)   +  H9. 

I  saline  and  Caustic  Potash.  Aniline. 


LESSON  XL. 

TURPENTINES   AND  CAMPHOR   GROUP.      This   series   of 
bodies  appears  to  contain  a  common  group  often  carbon  atoms, 


Elementary  Chemistry.  329 

and  affording  a  large  number  of  isomeric  derivatives.  It  is 
particularly  difficult  to  distingush  between  many  of  these 
bodies  which  appear  identical  in  their  chemical  relations,  but 
differ  in  their  physical  properties,  and  hence  are  said  to  be 
physical  isomers.  The  following  are  the  hydrocarbons  from 
which  these  substances  are  derived : 

CjO     Hl8  ClO    H.18  ClO    Hl4. 

Di-amylene  Camphene  Terebene  Cymol. 

or  and  its 

Menthene.  Isomers. 

These  hydrocarbons  yield  oxidized  products  termed  Cam 
phors  ;  we  thus  have — 

C10  H20  O         Cio  H18  O         C10  H,«  O         do  Hi*  O. 

Menthen-camphor.     Borneo-camphor.     Laurel- camphor.         Thymol  and 

Carvol. 

The  camphors  stand  in  the  same  relation  to  the  above 
hydrocarbons  as  benzyl  alcohol  stands  to  toluol.  By  a  further 
process  of  oxidation  acids  are  formed  ;  thus  we  have — 

Cio  Hie  terebene,  Cio  Hi6  O2,  camphinic  acid. 

Cio  Hie  O,  laurel  camphor,  Cio  Hi6  O4,  camphoric  acid. 

Turpentines  and  Isomers,  Ci0  H]6.  Oil  of  turpentine  of 
commerce  generally  consists  of  a  mixture  of  several  isomeric 
modifications  of  this  hydrocarbon.  It  is  obtained  from  several 
species  of  pine  ;  that  from  Pinus  nigra,  abies,  and  sylvestris 
constitutes  common  turpentine — that  from  the  larch  is  known 
as  venice  turpentine.  On  distillation  with  water  a  volatile 
aromatic  liquid  comes  over,  and  rosin  or  colophony  remains 
in  the  retort. 

The  best-known  natural  varieties  are  terebenthene  from  the 
Pinus  maritina,  boiling  at  161°,  and  possessing  a  power  of 
left-handed  polarization  of  — 42° -3  ;  austra-terebenthene,  from 
the  Pinus  Australis,  boiling  also  at  161°,  but  possessing  a 
right-handed  polarizing  power  of  +  2i°'5.  These  turpen 
tines,  when  heated,  or  when  acted  on  by  sulphuric  acids  and 
other  re-agents,  form  isomers  differing  in  their  action  on  the 
ray  of  polarized  light,  some  being  right-  and  some  left-handed, 


330  Elementary  Chemistry. 

whilst  others  are  inactive.  Terebenthene  combines  with 
hydrochloric  acid,  and  forms  isomeric  compounds  ;  it  also 
combines  with  water  to  form  a  solid  hydrate.  On  oxidation, 
the  turpentines  pass  into  resins. 

Many  essential  oils  are  isomers  of  turpentine  ;  of  these 
may  be  mentioned  essential  oil  of  lemons,  of  bergamotte, 
neroli,  lavender,  pepper,  camomile,  carraway,  cloves,  &c. 
These  often  contain  other  oxidized  oils  in  addition  to  the 
terebenes.  Of  these  bodies  laurel,  or  common  camphor, 
CioHieO,  is  the  most  important;  it  is  yielded  chiefly  by  the 
Laurus  camphora  of  China  and  Japan,  although  it  can  be 
obtained  from  other  plants.  Camphor  is  a  white,  crystalline, 
semi-transparent  mass  ;  it  fuses  at  175°,  and  boils  at  204°; 
it  is  soluble  in  alcohol,  and  its  solution  deviates  the  plane  of 
polarization  to  the  right  +  47° '4.  Camphor  dissolves  in 
alcoholic  potash  unaltered,  but,  on  heating,  is  first  converted 
into  Borneo  camphor,  Ci0Hi8O,and  afterwards  into  camphinic, 
CioHi6O2,  and  campholic  acid,  CioHi8O2.  On  boiling  with 
nitric  acid,  it  is  oxidized  to  camphoric  acid,  Cio  Hie  O4.  Like 
the  turpentines,  camphor  also  exists  in  several  physical  isomeric 
modifications,  which  chiefly  differ  in  their  action  on  polarized 
light.  The  camphoric  acid  obtained  from  these  different  cam 
phors  also  exhibit  differences  in  their  properties. 

Resins  and  Balsams. — Resin,  or  colophony,  is  obtained  in 
the  distillation  of  crude  turpentine  ;  the  other  resins,  such  as 
lac,  mastic,  copal,  &c.,  have  a  similar  composition.  They 
are  oxidation  products  of  the  terebenes. 

Caoutchouc,  or  India  Rubber,  and  Gutta  Percha.  —  T\\e  first 
of  these  is  a  compound  of  hydrogen  and  carbon,  and  is  an 
invaluable  substance  to  the  chemist ;  it  is  the  hardened  juice 
of  several  tropical  trees,  and  in  the  pure  state  is  white. 

Caoutchouc  combines  with  sulphur  in  various  proportions, 
forming  the  vulcanised  caoutchouc  of  commerce,  which  con 
tains  from  2  to  3  per  cent,  of  sulphur.  If  heated  more  strongly 
with  sulphur,  a  black,  horny  mass  called  ebonite  or  vulcanite, 
is  formed.  Gutta  percha  is  also  the  hardened  juice  of  a 
species  of  a  sapotacea,  growing  in  Borneo,  Singapore.  &c. 


Elementary  Chemistry.  331 

The  pure  substance  is  white,  and  insoluble  in  alcohol,  but 
soluble  in  ether. 

Naphthalin,  Cio  Us,  is  a  solid  hydrocarbon,  formed  in  large 
quantities  in  the  process  of  the  distillation  of  coal,  and  found 
in  the  heavy  oils  of  coal  tar.  It  is  also  formed  when  the 
vapors  of  many  organic  bodies,  such  as  alcohol  and  acetic 
acid,  are  passed  through  a  red-hot  tube.  Naphthalin  crystal 
lizes  in  pearly  white  plates,  which  dissolve  in  hot  alcohol 
and  cold  ether;  it  ftises  at  79° *2  and  boils  at  218°,  but  may 
be  sublimed  at  a  lower  temperature.  When  heated,  and  a 
light  applied,  it  burns  with  a  luminous  and  smoky  flame. 
Naphthalin  forms  with  strong  sulphuric  acid  two  compound 
acids,  corresponding  to  sulphovinic  acid.  Nitric  acid  attacks 
naphthalin,  forming  nitre-substitution  products,  and  also  an  acid 
termed  phthalic  acid,  C8HeO4 ;  this  substance  is  connected 
with  the  benzol  series,  inasmuch  as  on  heating  with  excess 
of  lime,  or  baryta,  it  is  converted  into  benzol: — 

C8H6Q4  =  C»04  +  C0H8. 

Phthalic  Acid.  Benzol. 

The  nitro-substitution  products  of  naphthalin  are  four  in 
number,  being  bodies  in  which  I,  2,  3,  or  4  atoms  of  hydrogen 
are  replaced  by  the  group  NO2.  From  nitro-naphthalin, 
CioH7(NO:;),  an  amido-naphthalin  is  formed  by  substitution  of 
NO2  by  NHa;  this  substance,  C10H7(NH2),  is  generally 
termed  naphthylamine.  Di-  and  tri-amido-naphthalin  are  also 
known.  The  chlorine  substitution  products  of  naphthalin  are 
very  numerous  bodies,  in  which  I,  2,  3,  4,  6,  and  8  atoms  of 
hydrogen  in  the  original  hydrocarbon  are  replaced  by  chlorine. 
A  second  series  of  chlorine  compounds  is  known,  which  are 
substitution  products  of  naphthalin  di-chloride,  CioHsCla. 

Nearly  connected  with  the  naphthalin  group  is  the  important 
coloring  matter  derived  from  madder,  and  termed  alizarin, 
CioHeOa.  This  substance  appears  not  to  be  contained  ready- 
formed  in  madder,  the  root  of  Rubia  tinctoria,  but  to  be  pro 
duced,  together  with  glucose,  from  a  body  termed  rubian  by 
the  action  of  acids,  alkalies,  and  ferments.  Alizarin  is 


332  Elementary  Chemistry. 

deposited  in  long,  red,  needle-shaped  crystals.  It  is  but 
very  slightly  soluble  in  cold,  but  more  soluble  in  hot  water, 
and  easily  dissolves  in  alcohol.  Alizarin  produces  insoluble 
red-colored  compounds  with  alumina  and  stannic  oxide,  which 
are  termed  lakes,  and  a  purple  or  black  compound  with  ferric 
oxide.  Hence,  in  calico  printing  solutions  of  these  oxides 
are  used  as  mordants,  and  are  printed  in  pattern  on  the  cotton 
cloth  which,  after  undergoing  certain  preparatory  processes, 
is  then  boiled  in  the  "dye-beck,"  containing  the  ground  mad 
der-root  mixed  with  water.  The  alizarin  of  the  madder  forms 
with  the  mordanted  cloth  an  insoluble  compound,  which  is 
colored  pink,  purple,  black,  or  chocolate,  according  as  the 
mordant  has  been  pure  alumina,  or  pure  iron,  or  a  mixture  of 
the  two.  Animal  fabrics,  such  as  silk  or  wool,  do  not  require 
the  application  of  mordants ;  they  are  able  alone  to  fix  and 
render  insoluble  the  coloring  matter. 

A  substance  isomeric  with  alizarin  has  been  artificially  pre 
pared  from  the  naphthalin  compounds  ;  it  crystallizes  in  yellow 
needles,  insoluble  in  water,  but  soluble  in  ether.  Mordanted 
cotton  cloth  cannot  be  dyed  with  this  compound,  but  silk  and 
wool  are  colored  yellow. 


VEGETO- ALKALOIDS. 

Under  this  name  a  series  of  bodies  containing  carbon, 
hydrogen,  oxygen,  and  nitrogen  is  grouped,  which  act  as 
bases,  and  are  found  in  certain  plants.  These  bodies,  for  the 
most  part,  have  not  been  artificially  prepared,  and  although  it 
is  believed  that  they  belong  to  the  class  of  compound  ammo 
nias,  yet  their  constitution  is  at  present  unknown.  Some  few 
of  the  alkaloids  are  liquid  and  volatile,  and  contain  only  car 
bon,  hydrogen,  and  nitrogen  :  these  have  a  more  simple  con 
stitution.  The  alkaloids  exert  a  powerful  influence  on  the 
ray  of  polarized  light,  some  deviating  the  plane  to  the  right 
and  some  to  the  left ;  they  also  combine  with  acids  to  form 
salts,  in  this  respect  resembling  ammonia,  thus  :- — 


Elementary  Chemistry.  333 

Type,  NH3  +  HC1  NH4C1  or  NH.HC1. 

dtHi.NOj  +  HC1  =  Ci7H20NO8Cl  or  CnH^NOaHCl. 

Morphine.  Morphine  Hydrochlorate. 

They  also  form  double  crystallizable  salts,  with  platinic 
chloride,  in  this  respect  again  resembling  ammonia.  The 
alkaloids  act  most  violently  on  the  animal  economy  ;  some, 
such  as  strychnine,  nicotine,  &c.,  form  the  most  violent  poisons 
with  which  we  are  acquainted,  whilst  others,  such  as  quinine 
and  morphine,  act  as  most  valuable  medicines. 

Alkaloids  containing  Carbon,  Hydrogen,  and  Nitrogen. 

Piperidine,  C8  Hn  N.  This  alkaloid  is  obtained  by  dis 
tilling  piperin,  d?  Hi9  NO3,  the  base  contained  in  black  pepper. 
Piperidine  contains  one  atom  of  hydrogen,  which  can  be 

f    T-T      ) 
replaced  by  an  alcoholic  group,  hence  its  formula  is    5     J^  (  N. 


It  is  a  colorless  liquid,  boiling  at  106°,  and  possessing  a  strong 
ammoniacal  odor  of  pepper. 

Conine,  C8  Hi6  N,  contained  in  the  hemlock,  Conium  macu- 
latum  ;  it  is  a  colorless  liquid,  boiling  at  212°,  and  has  a 
strong  alkaline  reaction,  forming  salts  with  acids.  Conine 
acts  as  a  narcotic  poison.  Under  certain  circumstances, 
conine  yields  butyric  acid,  by  oxidation. 

Nicotine,  do  Hi4  Na,  is  the  chief  alkaloid,  contained  in 
tobacco,  which  contains  varying  quantities,  from  2  to  8  per 
cent,  of  this  substance.  Nicotine  boils  about  240°,  under 
going  partial  decomposition,  but  it  may  be  distilled  in  an 
atmosphere  of  hydrogen  without  loss. 

Nicotine  is  soluble  in  water,  alcohol,  and  ether,  and  it  acts 
as  one  of  the  most  violent  poisons  with  which  we  are 
acquainted  ;  a  small  quantity  acting  on  the  motor  nerves, 
and  producing  convulsions  and  afterwards  paralysis.  Nicotine 
does  not  contain  any  hydrogen  replaceable  by  an  alcohol 
radical,  and  when  treated  with  iodide  of  ethyl,  a  salt  corre 
sponding  to  ammonium  iodide  is  produced  : 


334  Elementary  Chemistry. 

HI 

C6HT        ) 

in  r          T 

C5  H7        \  N'  I- 

2  (Ca  H5)  ) 

Ethyl-nicotine  Iodide. 

Alkaloids  containing  Carbon,  Hydrogen,  Oxygen,  and 
Nitrogen. 

Alkaloids  of  Opitun.  Opium  is  the  dried  juice  of  the  head 
of  the  poppy  (Papaver  somniferwri] ;  it  is  prepared  largely 
in  Asia  Minor,  Turkey,  Egypt,  and  India;  the  Smyrna 
opium  is  most  esteemed,  and  contains  from  10  to  15  per 
cent,  of  morphine.  There  are  no  less  than  six  different 
alkaloids  contained  in  opium  ;  of  the  semorphia  and  narcotine 
are  found  in  largest  quantity  : 

Morphine,  Ci7  Hi9  NO3.     Papaverine,  C20  H2i  NO4. 

Codeine  .  CJ8  H21  NO3.     Narcotine  .  C22  H23  NO7. 

Thebaine.  C19  H21  NO3.  Narceine  .  C23  H«  NO9. 
In  addition  to  these  substances,  opium  contains  a  neutral 
crystallizable  substance  called  Meconine,  Clo  Hi0  O4,  and  an 
acid  called  Meconic  Acid,  with  which  the  alkaloids  are  chiefly 
combined,  as  well  as  many  other  substances  in  small  quan 
tities,  besides  vegetable  matter,  &c.  These  alkaloids,  although 
possessing  a  very  closely  analogous  composition,  have  not 
yet  been  converted  one  into  the  other.  Opium  acts  as  a 
most  valuable  medicine,  in  small  doses  acting  as  a  sedative, 
although  heightening  the  pulse  and  the  action  of  the  heart. 
Taken  in  larger  doses  it  acts  as  a  narcotic  poison,  a  stupor 
and  prostration  soon  ensuing,  resulting  in  loss  of  all  voluntary 
power  of  motion,  complete  coma,  and  death.  It  appears  that 
thebaine  is  the  most  powerful  of  the  alkaloids,  then  papaverine, 
narcotine,  codeine,  and  morphine. 

Morphine,  Ci7  Hi9  NO3  +  H2O.  In  order  to  prepare 
morphia,  the  opium  is  extracted  with  water,  and  the  meconic 
acid  precipitated  by  calcium  chloride  ;  on  evaporating  the  fil 
trate,  crystals  of  morphine-hydrochlorate  separate  out.  Mor 
phine  dissolves  in  1,000  parts  of  cold  and  400  of  boiling 


Elementary  Chemistry.  335 

water  ;  hot  alcohol  dissolves  it  easily,  whilst  it  is  insoluble 
in  ether.  It  forms  crystalline  salts  soluble  in  water,  and  it 
appears  to  contain  no  replaceable  hydrogen  ;  as  an  ammo 
nium-iodide  is  obtained  when  it  is  acted  upon  with  ethyl 
iodide.  Small  quantities  of  morphine  can  easily  be  detected 
by  the  formation  of  a  deep  blue  coloration,  when  this  sub 
stance  comes  in  contact  with  ferric  chloride. 

Codeine,  Ci8  H2i  NO3  +  H2O,  is  left  in  the  mother  liquors 
from  which  the  morphine  has  crystallized.  Codeine  is  much 
more  soluble  in  water  than  morphine,  and  is  contained  in 
opium  in  much  smaller  quantities  ;  it  has  a  strong  alkaline 
reaction  and  neutralizes  acids. 

Thebaine,  d9H2i  NO3,  is  contained  in  very  small  quanti 
ties  in  opium  ;  its  poisonous  properties  are  more  violent  than 
any  other  of  these  alkaloids  ;  it  produces  tetanus. 

Papaverine,  C20  H2i  NC>4.  Distinguished  from  the  other 
opium  bases  by  giving  a  deep  blue  color  with  strong  sulphu 
ric  acid. 

Narcotine,  C22  H23  NO7,  remains  insoluble  when  opium  is 
treated  with  water,  and  it  is  obtained  by  dissolving  it  out 
from  the  "  marc "  or  insoluble  portion  of  the  opium  with 
hydrochloric  acid.  It  dissolves  in  128  parts  of  boiling  alco 
hol  and  19  of  boiling  ether.  Narcotine  when  heated  with 
potash  furnishes  ammonia  and  methylamine,  as  well  di-  and 
tri-methylamine  ;  and  when  treated  with  hydriodic  acid,  it 
furnishes  3  molecules  of  methyl  iodide  for  every  molecule  of 
narcotine. 

Alkaloids  of  the  Strychnos.  Two  alkaloids  possessing 
most  powerful  poisonous  properties,  and  called  Strychnine 
and  Brucine,  are  found  in  the  seeds  of  the  Strychnos  nux 
vomica,  and  in  the  Strychnos  Ignatius  or  the  St.  Ignatius's 
bean.  Strychnine,  C2i  H2a  N2O2,  is  a  base  forming  crystal- 
lizable  salts,  of  which  \\  per  cent,  is  contained  in  the  St. 
Ignatius's  bean.  It  acts  as  a  violent  poison,  producing 
tetanic  convulsions  ;  it  however  is  sometimes  given  in  very 
small  doses  in  medicine  ;  its  salts  are  all  extremely  bitter  and 
tart.  Strychnine  can  be  detected  when  present  in  minute 


336  Elementary  Chemistry. 

quantities,  by  yielding,  with  sulphuric  acid  and  potassium 
bichromate,  an  intense  purple  color,  which  passes  rapidly  into 
a  red,  and  then  into  a  yellow  color. 

Brucine,  C^  H-j6  N2  O4  +  4  H2O,  is  found  alone  in  false 
angustura  bark,  and  together  with  strychnine  in  nux  vovnica ; 
it  is  more  soluble  in  water  and  alcohol  than  strychnine. 
Brucine  and  its  salts  are  less  poisonous  and  less  bitter  than 
the  strychnine  compounds  ;  it  can  be  distinguished  from 
strychnine  by  the  bright  red  color  produced  when  this  sub 
stance  is  moistened  with  nitric  acid  ;  indeed  this  reaction  may 
also  be  employed  as  a  most  delicate  test  for  the  presence  of 
nitric  acid. 

Alkaloids  of  the  Chinchonas.  The  bark  of  this  species  of 
trees,  originally  grown  in  Peru,  but  now  transplanted  to  Java 
and  India,  contains  2.  alkaloids,  quinine  and  cinchonine.  and 
each  of  these  yields  2  isomeric  modifications,  quinidine  and 
quinicine  ;  cinchonidine  and  cinchonicine. 

The  Alkaloids  are  combined  in  the  bark  with  a  peculiar 
acid  termed  quinic  acid.  Quinine  is  a  most  valuable  medi 
cine,  acting  as  a  febrifuge  ;  cinchonine  does  not  possess  the 
same  valuable  properties. 

Quinine,  Cao  H24  N2Oo.  This  alkaloid  may  be  precipitated 
from  the  solution  of  its  sulphate  as  a  white  crystalline  powder. 
It  dissolves  in  350  parts  of  cold  water,  and  in  2  parts  of  alco 
hol.  Its  solution  has  a  strong  bitter  taste,  and  deviates  the 
plane  of  polarization  to  the  left.  Quinine  may  be  detected 
by  adding  chlorine-water,  and  afterwards  an  excess  of  ammo 
nia,  to  solutions  of  the  sulphate,  when  a  green  color  is  pro 
duced  ;  another  characteristic  reaction  consists  in  the  deep 
red  color  produced  when  finely  powdered  potassium  ferro- 
cyanide  is  thrown  into  the  solution  of  quinine  in  chlorine 
water.  Quinine  appears  to  possess  no  replaceable  hydrogen, 
as  when  treated  with  ethyl  iodide  a  salt  of  an  ammonium  com 
pound  is  formed.  Quinine  sulphate  is  the  salt  used  in  medi 
cine  ;  it  is  not  very  soluble  in  water,  but  dissolves  easily 
when  a  drop  or  two  of  sulphuric  acid  is  added.  Its  solution 
possesses  very  strongly  the  property  of  fluorescence. 


Elementary  Chemistry.  337 

Quinidine  and  Qidnicine.  The  first  of  these  isomers  of 
quinine  is  found  in  the  bark,  and  it  resembles  quinine  in  its 
febrifuge  qualities,  but  it  deviates  the  plane  of  polarization 
strongly  to  the  right.  Ouinicine  is  obtained  by  acting  upon 
quinine  by  heat.  It  is  a  bitter  substance,  possessing  a  semi- 
solid  resinous  consistency,  and  deviating  the  plane  of  polari 
zation  feebly  to  the  right. 

Cinchonine,  C20  H24  N2  O.  This  body  is  separated  from 
the  quinine,  which  accompanies  it,  by  its  less  solubility  in 
alcohol ;  thus  cinchonine  requires  30  parts  of  boiling  alco 
hol  for  solution,  and  therefore  crystallizes  out  whilst  the 
quinine  remains  in  solution.  Cinchonine  is  not  nearly  so 
powerful  a  febrifuge  as  quinine  ;  it  is,  however,  used  as  a 
medicine  in  some  countries.  Although  it  only  differs  from 
quinine  by  containing  one  atom  less  oxygen,  it  has  not  yet 
been  transformed  into  the  latter.  It  does  not  produce  a  green 
color  with  chlorine-water  and  ammonia  like  quinine  ;  it  acts 
as  a  strong  base,  and  forms  salts  which  are  more  soluble  in 
water  and  alcohol  than  those  of  quinine. 

Cinchonidint — Cinchonicine.     The  first  of  these  isomers  is 
found,  together  with  quinidine,  in  the  brown  resinous  mass 
left  after  the  extraction  of  the  two  chief  alkaloids.     It  pro 
duces  a  left-handed  rotation  on  a  polarized  ray,  whilst  cin 
chonine  produces  a  right-handed  polarization.     Cinchonicine 
is  obtained  by  heating  a  cinchonine  sulphate  to  120°  or  130°  ; 
it  deviates  the  polarized  ray  feebly  to  the  right :  hence  we  have 
Quinine         exerting  a  powerful  left-handed  rotation. 
Quinidine  "  powerful  right-handed      " 

Ouinicine  "  feeble       right-handed     " 

Cinchonine        "  powerful  right-handed      " 

Cinchonidine     "  powerful  left-handed         " 

Cinchonicine      "  feeble       right-handed      " 

Theobromine,  C7  H8  N4  O2,  the  crystallizable  alkaloid  con 
tained  in  cocoa  (Theobroma  Cacao).  If  in  this  substance  one 
atom  of  hydrogen  be  replaced  by  methyl,  Cafeine  is  formed. 

Cafeine,  or  Thelne,  C8  Hio  N4  O2  -f  H2O.  The  active 
IS 


338  Elementary  Chemistry. 

principle  of  tea  and  coffee  ;  also  found  in  the  leaves  of  Ilex 
Paraguayensis,  which  the  South  Americans  much  use  in 
place  of  tea  ;  also  in  guarana,  a  kind  of  chocolate  made  from 
the  fruit  of  Paulinia  Sorbilis.  The  quantity  of  the  alkaloid 
contained  in  tea  is  about  2  per  cent. ;  in  coffee,  o-8  to  I  per 
cent. ;  in  guarana  5  per  cent. ;  and  in  the  Paraguay  tea 
about  r2  per  cent. 

A  description  of  the  numerous  alkaloids  of  Jess  general 
interest  will  be  found  in  the  larger  manuals. 


LESSON  XLI. 
ALBUMINOUS  SUBSTANCES. 

Under  this  head  we  class  a  number  of  peculiar  compounds 
forming  a  characteristic  and  essential  portion  of  the  bodies 
of  animals,  and  occurring  also  in  certain  parts,  especially  the 
seeds,  of  vegetables.  These  compounds  possess  a  very  com 
plicated  constitution,  and  our  knowledge  of  their  true  chemi 
cal  relations  is  most  incomplete.  They  do  not  crystallize, 
and  exist  in  an  amorphous  jelly-like  form  ;  hence  it  is  very 
difficult  to  obtain  them  in  the  pure  state,  so  that  there  is  some 
doubt  even  about  their  chemical  composition.  They  all  con 
tain  sulphur,  and  most  of  them  phosphorus,  in  addition  to 
carbon,  hydrogen,  oxygen,  and  nitrogen,  and  in  their  different 
forms  possess  nearly  the  same  composition. 

Albumin  is  seen  in  one  of  its  purest  forms  in  the  white  of 
egg  ;  it  is  also  contained  in  the  serous  or  liquid  portion  of  the 
blood.  It  may  be  obtained  by  adding  acetic  acid  to  white  of 
egg  and  diluting  with  water,  when  a  white  flocculent  precipi 
tate  of  albumin  is  formed.  When  dried,  it  forms  a  yellow, 
transparent,  gum-like  mass  ;  this,  on  addition  of  cold  water, 
remains  as  a  white  insoluble  powder,  which,  like  the  precipi 
tated  albumin,  dissolves  in  water  containing  a  small  trace  of 
free  alkali.  One  of  the  most  characteristic  properties  of 
albumin  is  its  power  of  coagulation  ;  if  soluble  white  of  egg 


Elementary  Chemistry.  339 

be  heated  to  about  65°  C.,  it  becomes  solid  and  opaque  ;  in 
this  state  it  is  insoluble  in  water,  but  dissolves  in  dilute  alkali. 

Fibrin.  This  substance  exists  in  solution  in  the  blood,  but 
immediately  becomes  solid  when  the  blood  leaves  the  living 
body  ;  it  can  be  obtained  by  washing  the  clot,  or  thick  part  of 
blood,  until  the  red  color  has  disappeared,  or  it  may  be 
obtained  by  agitating  fresh  blood  with  twigs.  It  then  is 
obtained  in  the  form  of  colorless  filaments,  which  are  tasteless 
and  insoluble  in  water  ;  on  drying,  it  forms  a  horny  mass 
like  albumin.  The  fibrin  of  flesh  appears  to  differ  from  that 
of  blood  ;  and  differences  have  been  observed  between  the 
fibrin  from  arterial  and  that  from  venous  blood. 

Casein  is  the  nitrogenous  substance  contained  in  milk  and 
cheese  ;  it  closely  resembles  albumin  in  its  properties,  being 
coagulated  by  acids.  Casein  is  insoluble  in  pure  water,  but 
dissolves  in  a  very  dilute  solution  of  an  alkali.  In  milk  the 
casein  is  not  coagulated  by  boiling,  but  an  acid,  or  a  portion 
of  the  inner  coating  of  the  calPs  stomach,  called  rennet,  at 
once  separates  out  the  casein  and  butter  as  curds,  and  leaves 
the  milk-sugar,  and  salts  in  solution  as  whey. 

Vegetables  contain  similar  substances,  which  are  scarcely 
to  be  distinguished  from  the  bodies  derived  from  an  animal 
source.  Glutin,  or  the  sticky,  elastic  substance  contained 
with  starch  in  wheaten  flour,  is  vegetable  fibrin,  whilst  vege 
table  albumin  and  casein  occur  in  the  juices  and  seeds  of 
plants.  The  following  table  shows  the  percentage  composi 
tion  of  the  albuminous  bodies  ;  it  is  impossible  to  give  any 
formulae  for  these  complicated  substances  : 

Albumin.  Fibrin.  Casein. 

Carbon     .     .     .  53-5  527  53-8 

Hydrogen     .     .  7'o  6-9  7-2 

Nitrogen.     .     .  15-5  15-4  15-6 

Oxygen    .     .     .  22*0  23-5  22*5 

Sulphur    ...  i'6  1-2  0-9 

Phosphorus .     .  0-4  0-3  o'o 

lOO'O  lOO'O  lOO'O 


34°  Elementary  Chemistry. 

Gelatin  is  a  nitrogenous  substance  obtained  from  the  animal 
body  ;  it  is  prepared  by  boiling  the  tissues,  and  is  then  known 
as  glue,  isinglass,  or  gelatin ;  its  composition  is  the  same  as 
that  of  the  tissue  from  which  it  is  prepared. 

Animal  Chemistry  is  a  most  important  branch  of  chemical 
science,  and  one  which  unfortunately  is  but  very  slightly 
advanced  :  our  knowledge  of  the  composition  and  chemical 
constitution  of  the  substances  contained  in  the  animal  body  is 
very  incomplete,  and  concerning  many  of  the  chemical  changes 
which  occur  in  the  different  parts  of  the  animal  we  are  almost 
entirely  ignorant 

The  Bones  of  animals  consist  principally  of  tribasic  calcium 
phosphate,  together  with  a  kind  of  gelatin  ;  the  earthy  phos 
phate  dissolves  in  hydrochloric  acid,  leaving  the  bone  as  an 
elastic  gelatinous  mass  ;  when  burnt,  the  friable  and  earthy 
matter  alone  remains.  Bone  contains — 

Animal  matter 33 

Calcium  phosphate 57 

Calcium  carbonate 8 

Calcium  fluoride I 

Magnesium  phosphate      ....  I 

100 

The  Blood  of  animals  is  the  channel  by  means  of  which 
their  bodies  not  only  receive  all  the  requisite  supply  of  ma 
terials  for  their  growth  and  for  the  repair  of  waste,  but  by 
means  of  which  they  are  able  to  get  rid  of  the  worn-out 
matters  which  need  immediate  removal.  In  vertebrate  ani 
mals  the  blood  has  a  red  color  and  a  temperature  above  the 
medium  in  which  the  animal  lives  ;  in  mammalia,  and  espe 
cially  in  birds,  this  artificial  warmth  is  plainly  noticed.  The 
temperature  of  the  blood  is  singularly  constant  in  different 
animals  under  the  most  varying  conditions  of  climate  ;  it  is 
36°  9  (98°  F.)  in  man  and  42°'8  (or  109°  F.)  in  birds.  The 
chief  peculiarity  of  blood  is  the  existence  in  it  of  very  small 
round  or  oblong  discs,  differing  in  size  and  shape  in  different 


Elementary  Chemistry.  341 

animals  (diameter  0*0075  mm.  in  man,  and  four  times  as  large 
in  frogs).  These  are  called  the  blood-globules,  or  corpuscles  ; 
they  are  of  a  red  color,  and  float  in  a  colorless  liquid ;  when 
the  fibrin  coagulates  it  carries  down  with  it  mechanically  the 
red  globules. 

Healthy  human  blood  possesses  the  following  average  com 
position,  and  its  specific  gravity  is  1*055  : 

Coagulum,   j  Fibrine 0*30 ) 

or  clot.      ^Corpuscles 1270)    •>    * 

f  Water 79-00 1 

cprnrn  I  Albumin 7-00  I  « 

Serum.         <j  Fatty  matters  .     .     .     .     O-o6f87a 

L  Salts 0-94] 

The  color  of  the  blood  discs  is  due  to  a  substance  called 
hcematin;  this  contains  about  7  per  cent,  of  iron,  but  the  iron 
can  be  withdrawn  by  sulphuric  acid  without  any  apparent  al 
teration  of  the  red  coloring  matter.  Blood  is  charged  with 
dissolved  gases,  especially  oxygen,  nitrogen,  and  carbonic 
acid  ;  and  the  oxidation  of  the  tissues  is  effected  by  the  pres 
ence  of  the  former  gas :  the  arterial  blood  (freshly  oxidized 
from  the  lungs)  contains  in  100  volumes  14*5  volumes  of  nitro 
gen,  62*3  of  carbonic  acid,  and  23^2  of  oxygen  ;  whilst  in 
venous  blood  (charged  with  the  products  of  combustion  of 
the  body)  the  same  gases  are  found  in  the  proportion  of 
13*1,  7 1 '6,  and  15*3  volumes  respectively. 

Amongst  the  other  most  important  animal  fluids  may  be 
mentioned  Gastric  Juice,  a  clear  liquid  secreted  by  the  lining 
membrane  of  the  stomach  and  the  active  agent  in  effecting 
the  digestion  and  solution  of  the  albuminous  parts  of  the  food. 
It  has  an  acid  reaction  due  to  the  presence  of  free  lactic  and 
hydrochloric  acids.  The  Bile,  a  liquid  secreted  in  the  liver 
and  poured  out  into  the  duodenum  ;  this  substance  contains 
several  peculiar  nitrogenized  acids,  viz.,  taurocholic  acid 
C26  H45  N  SO7,  and  glycocholic  acid,  C,8  H43  N  O6.  A  pe 
culiar  substance  termed  taurin,  C2  H7  N  SO3,  is  obtained  by 
the  action  of  acids  on  bile ;  this  body,  which  is  isomeric  with 


342  Elementary  Chemistry. 

the  compound  of  aldehyde  ammonia  with  sulphurous  acid, 
can  be  prepared  artificially  by  heating  ammonium-isethion- 
ate,  H4  N  Ca  H6  S  O4,  which  parts  with  Ha  O,  and  forms 
taurin. 

Milk.  The  composition  of  this  important  secretion  varies 
considerably  in  different  animals,  but  each  kind  contains  all 
the  materials  needed  for  the  formation  of  the  body  of  the 
young  animal ;  thus  it  contains  casein  (a  body  having  nearly 
the  same  composition  as  flesh),  fats  (butter),  and  milk  sugar, 
together  with  those  inorganic  salts,  especially  the  alkaline 
chlorides,  and  calcium  phosphates,  needed  for  the  formation 
of  bone.  The  following  gives  the  average  composition  of 
milk  of  different  animals  : — 

Woman.  Cow.  Goat.  Ass.  Bitch. 

"Water 88'6  87-4  82*0  90-5  66-3 

Butter 2'6  4-0  4-5  1-4  14-8 

Milk  Sugar  and  Soluble  Salts. ..           4'o  5*0  4-5  6 '4  z'g 

Casein  and  Insoluble  Salts 3*9  3-6  9'o  rj  i6'o 

The  specific  gravity  of  milk  varies  from  I  -03  to  I  -04. 

The  Urine.  It  is  in  the  urine  that  a  large  portion  of  the 
waste  nitrogenous  portions  of  the  body  pass  off  as  urea  and 
uric  acid  ;  the  urine  is  secreted  by  the  kidneys  from  the 
arterial  blood.  Healthy  urine  contains,  in  1,000  parts,  957 
parts  of  water,  14  of  urea,  I  of  uric  acid,  15  of  other  organic 
matter,  and  13  of  inorganic  salts. 

Functions  of  Animals  and  Plants. 

The  general  characteristics  of  animal  and  'vegetable  life 
may  be  stated  as  follows  :  the  animal  lives  upon  organized 
materials,  taking  up  oxygen  and  evolving  carbonic  acid  and 
other  oxidized  products  ;  the  plant  lives  upon  unorganized 
materials,  especially  carbonic  acid,  water,  ammonia,  and  salts, 
organizing  them  and  evolving  oxygen.  The  chemical  func 
tion  of  the  animal  is  oxidation,  that  of  the  plant  reduction. 
The  food  of  the  plant  serves  merely  to  increase  its  bulk  ; 
that  of  the  animal  is  employed  (after  it  has  attained  its  full 


Elementary  Chemistry.  343 

growth)  to  replace  the  material  worn  out  by  all  the  active 
operations  of  life.  The  animal  obtains  the  energy  necessary 
for  its  existence  from  the  oxidation  of  its  own  body  ;  the 
plant  obtains  the  energy  necessary  for  the  organization  of  its 
food  directly  from  the  sun. 

Respiration  and  Animal  Heat.  The  process  of  respira 
tion,  essential  to  the  life  of  all  animals,  consists  in  the  aera 
ting  of  the  blood  circulating  through  the  lungs  or  similar  appa 
ratus,  by  means  of  the  oxygen  of  the  air.  The  blood  does 
not  come  into  actual  contact  with  the  air,  but  is  separated  by 
a  large  surface  of  very  thin  membrane,  through  which  the 
exchange  of  gases  takes  place  by  solution  and  diffusion. 
Not  only  does  the  blood  gain  in  oxygen  (see  Blood,  p.  340), 
but  it  loses  the  products  of  combustion  with  which  it  is 
charged,  and  is  thus  rendered  fit  again  to  circulate  and  carry 
away  used-up  material.  The  volume  of  air  thrown  out  of  the 
human  lungs  at  each  ordinary  expiration  amounts  to  from  350 
to  700  cubic  centimeters  :  this,  however,  by  no  means  empties 
the  lungs,  whose  capacity  is  much  greater  ;  the  number  of 
respirations  amounts  to  about  fifteen  in  each  minute.  The  - 
expired  air  differs  remarkably  from  the  inspired  air,  as  it  con-  <J 
tains  from  3  to  6  per  cent,  of  carbonic  acid,  and  will  not  sup-  <• 
port  the  combustion  of  a  candle. 

Under  different  circumstances  of  health  or  disease,  activity 
or  repose,  sleeping  or  waking,  after  a  meal  or  fasting ;  ac 
cording  to  the  temperature,  pressure  of  the  air,  and  from 
other  varying  conditions,  the  quantity  of  exhaled  carbonic 
acid  varies  considerably.  The  determination  of  the  quantity 
of  carbonic  acid  exhaled  by  an  animal  under  the  above  cir 
cumstances  is  a  subject  of  the  highest  importance,  but  one 
which  is  surrounded  by  numerous  experimental  difficulties. 
We  may  assume,  as  the  result  of  the  best  experiments,  that  a 
man  gives  off  19-8  litres  of  carbonic  acid  (at  o°  and  760  mm.) 
each  hour  ;  this  amounts  to  about  40  grms.  of  carbonic  acid, 
or  ii  grm.  of  carbon  per  hour:  the  heat  which  is  always 
evolved  by  the  combustion  of  this  carbon  goes  to  keep  up 
the  temperature  of  the  body.  It  is  difficult  to  determine  with 


344  Elementary  Chemistry. 

accuracy  how  far  the  whole  of  the  animal  heat  can  be  ac 
counted  for  by  the  combustion  of  this  carbon,  as  the  chemical 
changes  which  go  on  in  the  body  are  of  a  very  complicated 
nature,  and  as  yet  little  understood.  Considering,  however, 
the  subject  in  a  general  point  of  view,  there  cannot  be  much 
doubt  that  the  whole  of  the  animal  heat  is  derived  from  the 
combustion  of  the  materials  of  the  body  ;  thus  we  find  that  in 
birds,  whose  temperature  is  higher  than  that  of  mammalia, 
the  quantity  of  carbonic  acid  evolved  is  more  than  half  as 
much  again  as  in  larger  animals  ;  whilst  in  cold  climates, 
where  the  loss  of  animal  heat  is  great,  men  find  it  necessary 
to  eat  enormous  quantities  of  fat,  this  doubtless  serving  to 
maintain  the  temperature  of  the  body. 

The  effect  of  starvation  on  the  quantities  of  carbonic  acid 
and  urea,  taken  as  representing  the  rate  of  change  going  on 
in  the  body,  is  very  remarkable ;  in  a  dog,  the  quantity  of 
carbonic  acid  was  reduced  by  fasting  for  ten  days  to  one-third, 
and  the  urea  to  one  twenty-second  part  of  the  amount  given 
off  on  full  diet ;  whereas  in  a  man  the  carbonic  acid  was 
nearly  reduced  to  one-third  by  starvation.  An  interesting 
fact  has  been  observed,  viz.,  that  hydrogen  and  marsh-gas 
are  evolved  in  small  quantities  from  the  skin  and  lungs  under 
certain  conditions.  This  subject  is  quite  in  its  infancy,  and 
demands  careful  experimental  investigation,  as  it  is  by  such 
patient  research  alone  that  we  can  hope  to  form  any  real 
estimate  of  the  income  and  expenditure  of  the  body.  The 
special  study  of  the  chemistry  of  the  body  has  been 
made  a  separate  branch  science,  termed  Physiological 
Chemistry. 

Food  of  Plants.  Animals,  as  we  have  seen,  are  unable  to 
produce  the  complicated  chemical  compounds  which  they 
need  for  their  structure  ;  plants  are,  however,  able  to  do  this, 
and  from  the  elementary  constituents  to  build  up  their  various 
parts.  This  function  of  plants  is  entirely  dependent  upon  the 
sunlight ;  without  sunlight  the  green  coloring  matter  of  the 
leaves  of  plants  cannot  decompose  the  atmospheric  carbonic 
acid,  and,  therefore,  without  sunlight,  the  plant  cannot  grow. 


Elementary  Chemistry.  345 

In  order  to  separate  the  atoms  of  carbon  and  oxygen,  an 
expenditure  of  force  is  necessary ;  this  force  is  derived  from 
the  rapidly  vibrating  solar  rays  ;  it  is  they  which  tear  asunder 
the  carbon  and  oxygen  atoms,  and  thus  enable  the  leaves  to 
take  up  and  assimilate  the  carbon,  throwing  out  the  oxygen 
into  the  air  for  the  subsequent  use  of  animals.  When  vege 
table  matter  is  ignited,  it  burns  to  carbonic  acid,  and  generates 
exactly  the  same  amount  of  force,  as  the  vibrations  of  heat, 
which  were  needed,  in  the  form  of  vibrations  of  light,  originally 
to  decompose  the  atmospheric  carbonic  acid.  Hence  when 
coal  burns,  the  light  and  heat  evolved  may  truly  be  said  to  be 
that  of  the  sun;  and,  as  animals  depend  for  their  existence 
upon  vegetables,  and  these  in  their  turn  cannot  live  without 
the  solar  radiations,  animals  may  with  truth  be  called  children 
of  the  sun. 

The  bodies  of  plants  may  be  considered  to  be  composed  of 
two  kinds  of  substances,  organic,  such  as  starch,  vegetable 
fibre,  &c. ;  and  inorganic  salts,  constituting  the  ash  of  the 
plant.  The  carbon,  needed  for  the  first  of  these  materials, 
the  plant  obtains  mainly  from  the  atmosphere  ;  the  nitrogen, 
hydrogen,  and  oxygen,  which  the  organic  substances  contain, 
the  plant  takes  up  both  by  its  leaves  and  by  its  roots  ;  whilst 
the  whole  of  the  inorganic  salts  are  absorbed  from  the  earth 
by  the  roots,  which  act  as  the  mouth  of  the  plant,  whilst  the 
leaves  may  be  compared  to  the  lungs  of  animals.  Every  plant 
has  in  the  atmosphere  an  unlimited  supply  of  carbon  and 
water ;  but  for  the  supply  of  inorganic  materials,  the  plant  is 
dependent  upon  the  nature  of  the  particular  soil  upon  which 
it  grows.  Plants  possess  the  peculiar  power  of  selection,  by 
the  roots,  of  the  mineral  constituents  of  food,  as  well  as  the 
subsequent  chemical  elaboration  of  the  materials.  Of  the 
causes  of  the  changes  which  thus  go  on  we  know  nothing : 
thus  we  cannot  explain  why  an  acorn  turns  out  always  to  be 
an  oak,  or  why  of  two  seeds  sown  in  the  same  soil  and  exposed 
to  the  same  sunlight  and  air,  one  evolves  a  poisonous  and  the 
other  a  wholesome  plant. 

Concerning  the  growth  of  plants  a  large  amount  of  infor- 
15* 


346  Elementary  Chemistry. 

mation  has  been  amassed,  but  we  are  far  from  possessing 
even  an  approach  to  a  knowledge  of  the  laws  which  regulate 
this  important  subject  For  an  account  of  the  interesting 
facts  which  have  been  ascertained  respecting  the  questions  of 
manuring,  fertility  of  the  soil,  &c.,  we  must  refer  the  reader 
to  books  on  the  branch  science  of  Agricultural  Chemistry. 


Elementary  Chemistry. 


347 


b  b  b  b  b  b  o  \o 


T 

8    0    0    J  ^VD  00    M 

o  b  b  b  ^  J^.~ 


11 

wg 


^^2  8 


v 
b  o  b  '*,  b  »  « 

- 


28^ 


f,  o  0s  N  O  Q 
O  O  G^  <^  O 
O  oo  O  c^  M 


M 
Kilometre. 


u  u 

JlJeilll 


2"? 


*! 


* 


8  S 
o  b 


8457 
5724 
2398 


10-76 
1076-42 
07642-99 


hi 

£§8" 

el  8 


Centiare  or 
Are  or  100 
Hectare  or 


343 


Elementary  Chemistry. 


.51*8 

-SHHss 

d 

ilfftHf 

•g^  r  c 

8  ^"  £r  £  £  «  1  °°" 

cO  ?"s 

§  8  8  §  8  o"^c»" 

•s"Jj 

b  b  b  b  b  'N  Y«.»o 

1 

li  "'^ 

b  b  b  b  b  b  b  b 

;e£jj 

I  If  !l!!l 

1 

,. 

is  mill 

|i 

^S  -"»5 

8  Q  cl  8  o  cf'o-S 

IS 

^"^  ^-.S 

2  Q  Q  §  8  ^^^ 

^^ 

Ooo  £o 

-"«! 

b  b  b  b  «  V,  g  g 

^     S 

iD6ii£S 

^  II  11° 

b  b  b  o  b  b  b  b 

If 

,l| 

txvO   O    rx  r^  r^i  •**-  i-t 

(-0 

'IL 

Q    O    O    N   (N    O    -^-O 

II  II 

5S 

000.   j,^|. 

I 

|j| 

b  b  b  b  b  b  Vi  Vj 

1^ 

u 

•^  <" 

H 

Ch-3 

£cj 

s  2i 

DC 

M      M 

C) 

O  *ti 

o 

•g-y 

M   ^ 

O     y* 

f^i  N   M*1  if)  n*  t^  rT\n* 

IX 

£"§  rf 

f 

M 

u 

o   o1  £n  £  2,^^ 

0 

•JcxoJ: 

.0.8.8  l?«y?«V8 

h 

?>^ 

b  b  b  b  b  V.  N  M 

fa 
O 

cj  £~ 

'"S 

5; 

O 

1* 

M 

Crt 

a 

£  II 

u 

w 

^  II 

0^ 

c 

>-~J 

p 

cTr^n^to^InM^n^ 

tn  0 

en 

r^  c?  r^s  ^oo  <Xt   8    8 

CO 

w 

Is 

Onrx.oiO'-'<o>H 

.£     M 

a 

'!>  B 

(§1 

fslfpff 

E  E 
E  £ 

^  so    2    o 

W    )?  i?)  ? 

OO 

\O       M 

O 

HH 

M     *O 

o 

o 

a 

e^vo 

3 

:  :  :     :     :  : 

S 

:  :  :  :  : 

fs 

;§8   i  si 

| 

II   II 

£1.1     !    li 

•b 

:  :  :  :  : 

g 

£  c  S  u  '    •"  : 

II 

.£  >, 

^ 

rt  0 

!^i8K 

3 

U 

iti  ':  i  ^  ^  % 

iii  °iiii 

III  111  II 

iJiSallll- 

?3g£2^iJ  ~  >, 
JSoCOQffii^S 

Elementary  Chemistry.  349 


QUESTIONS  AND  EXERCISES  UPON  THE  FORE 
GOING  LESSONS. 

IN  order  to  enable  the  pupil  to  master  the  principles  of  the 
science,  he  must  conscientiously  write  out  answers  to  the 
Questions,  and  work  out  the  Exercises  given  in  illustration 
of  each  Lesson. 

LESSON  I.     Introduction. 

1.  Describe  an  experiment  to  prove  that  when  a  candle 
burns,  the  materials  are  not  annihilated. 

2.  Distinguish  between  a   chemical  element  and  a  com 
pound. 

3.  What  is  the  construction  and  use  of  a  chemical  balance  ? 

4.  Name  a  few  important  elements. 

5.  Is  it  likely  that  we  are  now  acquainted  with  all  the 
elements  existing  on  the  earth,  and  why  ? 

6.  Describe  some  cases  in  which  chemical  actions  occur. 

LESSON  II.     Oxygen  and  Hydrogen. 

1.  How  did  Priestley  first  prepare  oxygen  gas  ? 

2.  Describe  the  process  now  adopted  for  obtaining  this  gas. 

3.  Whence  is  the  name  oxygen  derived  ? 

4.  State  the  action  produced  (i)  by  animals,  (2)  by  plants, 
on  the  air. 

5.  Learn  by  heart  the  composition  by  weight  of  potassium 
chlorate. 

6.  I  want   100  pounds  of  oxygen  ;  how  many  pounds  of 
potassium  chlorate  must  I  take  ? 

7.  What  is  meant  by  the  combining  weights  of  the  ele 
ments  ?     Give  an  example. 

8.  How  can  hydrogen  be  obtained  from  water  ? 


350  Elementary  Chemistry. 

9.  Mention  the  chief  properties  of  hydrogen. 

10.  What  is  formed  when  hydrogen  burns  in  the  air  ?     How 
can  this  be  exhibited  ? 

11.  65-2   parts  by  weight  of  zinc  in  decomposing  water 
yield  2  parts  by  weight  of  hydrogen.     How  much  zinc  must 
be  employed  to  obtain  100  pounds  of  hydrogen  ? 

12.  What  is  the  derivation  of  the  word  hydrogen  ? 


LESSON  III.     Chemical  Calculations,  &c. 

[It  will  generally  be  found  necessary  to  divide  this  into 
several  lessons,  and  to  familiarize  the  pupil  to  the  subject  by 
a  much  larger  number  of  exercises  than  those  here  given.] 

1.  Describe    shortly  the  metrical  system  of  weights   and 
measures. 

2.  How  many  cubic  centimetres  are  contained  in  i  cubic 
metre  ? 

3.  How  is  a  thermometer  made  and  graduated  ? 

4.  Describe  the   three  thermometric   scales   now   in   use. 
Work  out  the  following : 

How  many  degrees  C.  and  R.  correspond  to  +    42°  and  —    32°  Fah.  ? 
C.  and  F.          "  +  V7°  and  —      2°  R.  ? 

F.  and  R.         "  +    78°  and  —  172°  C? 

5.  If  273  volumes  of  gas  be  at  the  temperature  of  o°  C,  to 
what  temperature  must  they  be  heated  in  order  to  expand  to 
295  volumes  ?     ',.  "I 

6.  What  volume  will  1,063  litres  of  hydrogen  at  -2°  occupy 
when  heated  to  100°  ? 

7.  State  Boyle's  Law  of  Pressures. 

8.  What  volume  will  1,000  cbc.  of  oxygen   at  o°  and  760 
mm.  become  at  a  temperature  of  i6°'5,  and  under  a  pressure 
of  735  mm.  ?     <\\*^  & 

9.  Learn  by  heart  the  weight  in  grammes  of  one  litre  of 
hydrogen  at  o°  and  under  760  mm.  pressure. 

10.  What  simple  method  is  used  for  calculating  the  weight 


Elementary  Chemistry.  351 

of  one  litre  of  the  elementary  gases  at  the  standard  tempera 
ture  and  pressure  ? 

11.  How  many  cubic  centimetres  of  oxygen  gas  measured 
at  10°  and  under  745  mm.  pressure  can  be  got  by  heating  20 
grammes  of  potassium  chlorate  ? 

12.  What  is  the  weight  in  grammes  of  516  litres  of  hydro 
gen  gas  measured  at  —  20°  and  under  770  mm.  pressure  ? 


LESSON  IV.     Water. 

[It  may  be  necessary  to  divide  this  into  two  or  more  les 
sons.] 

1.  How  did  Cavendish  determine  the  composition  of  water  ? 

2.  Describe  the  most  exact  methods  of  determining   the 
composition  of  water  (i)  by  volume,  (2)  by  weight. 

3.  What  is  meant  by  the  latent  heat  of  water  ?     How  is 
this  determined  ? 

4.  How  can  you  show  that  when  a  liquid  solidifies,  heat  is 
given  out  ? 

5.  Describe   the  changes  in  bulk  which  water  undergoes 
when  heated  from  o°  to  100°. 

6.  When  does  water  boil  ? 

7.  How  is  the  latent  heat  of  steam  determined  ? 

8.  Define  the  term  "  thermal  unit." 

9.  How  is  the  tension  of  aqueous  vapor  measured  ? 

10.  Why  must  the  barometric  pressure  be  noticed  when 
graduating  a  thermometer  ? 

11.  How  is  pure  water  obtained  ? 

12.  What  is  the  composition  of  hydric  peroxide  ? 


LESSON  V.     The,  Atmosphere. 

1.  How  may  pure  nitrogen  gas  be  prepared  ? 

2.  What  is  the  mean  height  of  the  barometer  at  the  sea's 
level  ? 


352  Elementary  Chemistry. 

3.  Why  does  water  boil  at  a  lower  temperature  than  100° 
on  a  mountain  top  ? 

4.  What  reasons  have  we  for  believing  that  the  air  is  a  me 
chanical  mixture,  and  not  a  chemical  combination  of  nitrogen 
and  oxygen  ? 

5.  Describe  the  mode  of  making  a  eudiometric  analysis  of 
the  air. 

6.  How  may  we  determine  the  composition  of  the  air  by 
weight  as  regards  nitrogen  and  oxygen  ? 

7.  Draw  and  describe  an  apparatus  for  estimating  the  quan 
tity  of  carbonic  gas  contained  in  the  air. 

8.  What  important  part  does  this  carbonic  acid  play  as  re 
gards  vegetation  ? 

9.  How  is  rain  formed  ? 

10.  Explain  the  formation  of  dew  and  hoar  frost. 

11.  What  is  the  use  of  hygrometers  ? 

12.  Name  other  constituents  of  the  atmosphere. 


LESSON  VI.     Nitric  Acid  and  Oxides  of  Nitrogen. 

1.  Give  the  composition  by  weight  of  the  five  oxides  of  ni 
trogen. 

2.  Explain  what  is  meant  by  chemical  combination  in  mul 
tiple  proportions. 

3.  State  the  principles  of  Dalton's  atomic  theory. 

4.  What  happens  when  electric  sparks  are  passed  through 
the  air  ? 

5.  Learn  by  heart  the  combining  weights  of  oxygen,  hydro 
gen,  nitrogen,  chlorine,  potassium,  sulphur  ;  and  the  formulas 
of  nitric  acid,  sulphuric  acid,  nitre,  and  potassium  sulphate. 

6.  Write  out  in  symbols  the  decomposition  occurring  in  the 
preparation  of  nitric  acid,  and  explain  the  meaning  of  these 
symbols. 

7.  I  want  500  grms.  pure  nitric  acid  ;  how  many  grms.  of 
nitre  and  sulphuric  acid  shall  I  need,  and  how  many  grms.  of 
hydric  potassium  sulphate  will  remain  ? 


Elementary  Chemistry.  353 

8.  Mention  the  tests  for  nitric  acid. 

9.  How  is  nitric  pentoxide  prepared  ? 

10.  100  parts  by  weight  of  this   substance  contain  25*93 
parts  of  nitrogen,  and  74/07  parts  of  oxygen.     Show  that  the 
formula  of  the  substance  is  N2  O6. 


LESSON  VII.     Oxides  of  Nitrogen  and  Ammonia. 

1.  Name  the  chief  properties  of  laughing  gas. 

2.  How  many  grms.  of  nitrous  oxide  and  water  can  be 
obtained  from  213  grms.  ammonium  nitrate  ? 

3.  How  is  the   composition  by  volume  of  nitrous   oxide 
determined  ? 

4.  I  want  100  litres  of  nitric  oxide  gas  when  the  tempera 
ture  is  o°  and  the  pressure  760  mm.      What  weight  in  grms. 
of  copper  and  nitric  acid  must  I  take  ? 

5.  Point  out  the  relation  between  nitric  pentoxide  and  the 
nitrates,  and  nitric  trioxide  and  the  nitrites. 

6.  Give  the  formulae  representing  three  different  modes  by 
which  ammonia  can  be  produced. 

7.  How  many  litres  of  ammonia  measured  at  10°  and  under 
a  pressure  of  755  mm.  can  be  obtained  from  100  grms.  of  sal 
ammoniac. 

8.  Describe  the  principles  of  Carry's  freezing  machine. 

9.  How  is  the  composition  by  volume  of  ammonia  ascer 
tained  ? 

10.  How  can  ammonia  be  liquefied  ? 

LESSON  VIII.     Carbon  and  Carbonic  Acid. 

1.  Name    the    three   allotropic    modifications   of   carbon. 
State  their  chief  peculiarities. 

2.  Give  a  short  description  of  the  nature  of  coal.      What 
changes  have  occurred  in  the  passage  of  wood  into  coal  ? 

3.  Required    562   grms.    carbonic   dioxide  ;  how   will  you 
obtain  it,  and  what  weight  of  materials  will  you  need  to  use  ? 


354  Elementary  Chemistry. 

4.  What  law  regulates  the  absorption  of  this  gas  in  water  ? 

5.  How  can  carbonic  dioxide  be  obtained  in  the  liquid  and 
in  the  solid  state  ?      What  peculiar  property  does  this  liquid 
exhibit  ? 

6.  Explain  the  mode  adopted  for  obtaining  very  low  tem 
peratures  by  means  of  solid  carbonic  acid. 

7.  Describe,  with  a  drawing,  the  apparatus  used  to  deter 
mine  the  composition  of  carbonic  acid. 

8.  State  the  results  of  this  determination. 

9.  How  many  litres  of  carbonic  dioxide  measured  at  300°, 
and  under  a  pressure  of  740  mm.  can  be  obtained  by  burning 
one  kilogramme  of  Wigan  cannel  (No.  5  on  page  69)  ? 

10.  Show,   by   describing    an    experiment,    that    carbonic 
dioxide  contains  its  own  volume  of  oxygen. 


LESSON  IX.     Carbonic  Oxide  and  Hydrocarbons. 

1.  How  many  grms.  of  carbon  will  be  needed  to  convert 
100  litres  of  carbonic  dioxide  at  o°  and  760  mm.  into  carbonic 
oxide,  and  how  many  litres  of  this  latter  gas  will  be  formed  ? 

2.  Find  the  volume  in  litres  at  10°  and  740  mm.  of  carbonic 
oxide  which  can  be  obtained  from  100  grms.  of  oxalic  acid 
and  formic  acid  respectively. 

3.  What  is  formed  when  caustic  potash  and  carbonic  oxide 
are  heated  together  ? 

4.  How  is  the  composition  of  carbonic  oxide  ascertained  by 
eudiometric  analysis  ? 

5.  What  is  the  composition  of  marsh-gas  and  fire-damp  ? 

6.  How  is  olefiant  gas  prepared  ? 

7.  State  shortly  the  properties  and  composition  of  coal  gas. 

8.  How  is  the  illuminating  power  of  coal  gas  ascertained? 

9.  Describe  the  construction  of  a  Bunsen's  burner. 

10.  Explain  the  principles  of  the  Davy  lamp. 

11.  How  many  litres  of  carbonic  acid  are  formed  by  the 
combustion  of  one  litre  of  olefiant  gas  ? 

12.  How  is  cyanogen  gas  prepared  ? 


Elementary  Chemistry.  355 

13.  I  want  50  grms.  pure  hydrocyanic  acid  ;  how  many 
grms.  of  potassium  cyanide  and  sulphuric  acid  shall  I  need  to 
use? 

LESSON  X.     Chlorine. 

1.  Write  down  as  an  equation  the  decompositions  which 
occur  in  the  preparation  of  chlorine  from  rock  salt. 

2.  I  want   100  litres  of  chlorine  gas  at  10°,  and  under  the 
pressure  of  735  mm. ;  how  many  grms.  of  the  materials,  viz., 
Na  Cl,  H2  SO4,  and  Mn  O2  shall  I  require  ? 

3.  Describe  experiments  proving  the  power  of  chlorine  to 
combine  with  hydrogen. 

4.  Explain  the  bleaching  action  of  chlorine. 

5.  How  many  kilos,  of  salt  and  sulphuric  acid  must  be  taken 
to  yield   100  kilos,  of  aqueous  hydrochloric  acid  containing 
20-22  per  cent,  of  the  gas  ? 

6.  How  is  the  composition  of  hydrochloric  acid  determined  ? 

7.  Write  out  the  formulas  of  the  oxides  of  chlorine  and  the 
corresponding  acids. 

8.  Describe  the  action  of  water  upon  hypochlorous  oxide, 
nitric  pentoxide,  and  carbonic  dioxide. 

9.  What  is  the  composition  of  bleaching-powder  ? 

10.  How  is  potassium  chlorate  prepared  ? 

11.  Show  from  the  composition  of  the  salt  that  the  formula 
of  potassium  chlorate  is  K  Cl  O3. 

12.  Show  that  the  aqueous  perchloric  acid  containing  72-3 
per  cent,  of  H  Cl  O4  does  not  correspond  to  any  definite  com 
pound  of  this  acid  with  water. 


LESSON  XI.     Bromine,  Iodine,  and  Fluorine. 

1.  Describe  the  mode  of  obtaining  pure  bromine. 

2.  What  is  the  composition  of  bromic  and  perbromic  acids  ? 

3.  Write  out  in  an  equation  the  decompositions  occurring  in 
the  manufacture  of  iodine  from  potassium  iodide. 


356  Elementary  Chemistry. 

4.  How  is  hydriodic  acid  gas  prepared  ? 

5.  Show  that  the  aqueous  hydriodic  acid,  boiling  at  a  con 
stant  temperature,  and  containing  57  per  cent,  of  H  I  does  not 
correspond  to  a  definite  hydrate. 

6.  How  would1  you  detect  iodine,  bromine,   and  chlorine 
when  present  in  solution  together  ? 

7.  How  can  fluorine  be  prepared  ? 

8.  Mention  the  most  remarkable  property  of  H  F. 

9.  State  the  general  relations  which  Cl,  Br,  I,  and  F  exhibit 
amongst  themselves. 


LESSON  XII.     Sulphur  and  Sulphurous  Acid. 

1.  State  the  different  compounds  in  which  sulphur  is  met 
with  in  nature. 

2.  Name  some  of  the  chief  properties  of  sulphur. 

3.  Write  down  the  names  and  symbols  of  the  compounds 
of  sulphur,  oxygen,  and  hydrogen. 

4.  How  is  sulphuric  dioxide  prepared  ?     How  can  it  be 
liquefied  ? 

5.  How  many  cubic  centimetres  of  sulphuric  dioxide  at  o° 
and  760  mm.  can  be  got  by  the  use  of  12  grms.  of  copper,  and 
how  many  grms.  of  sulphuric  acid  will  be  needed  ? 

6.  How  is  real  sulphurous  acid  formed  from  sulphuric  di 
oxide  ?    Explain  the  constitution  of  the  salts  termed  sulphites. 

7.  How  does  sulphurous  acid  act  as  a  bleaching  agent  ? 


LESSON  XIII.     Sulphuric  Acid  and  Sulphuretted 
Hydrogen. 

1.  How  is  sulphuric   trioxide  prepared,  and  what  are  its 
properties  ? 

2.  Describe  the  decompositions  by  which  sulphuric  acid  is 
prepared  in  the  leaden  chamber. 

3.  How  many  tons  of  chamber-vitriol,  containing  70  per 


Elementary  Chemistry.  357 

cent  of  real  acid  (H2  SO4),  can  be  prepared  from  250  tons  of 
pyrites,  containing  42  per  cent,  of  sulphur  ? 

4.  What  is  meant  by  the  term  "  molecule  "  as  distinguished 
from  "  atom  ?  " 

5.  How  many  grms.  of  oxygen  can  be  obtained  by  the  de 
composition  of  450  grammes  H2  SO4  at  a  red  heat  ? 

6.  Explain  what  is  meant  by  the  terms  "  monatomic  "  and 
"  di-atomic." 

7.  How  would  you  detect  the  presence  of  sulphuric  acid  ? 

8.  What  is  the  composition  of  sodium  hyposulphite  ? 

9.  How  is  sulphuretted  hydrogen  prepared  ? 

10.  Explain  how  this  gas  may  be  used  for  the  separation 
of  the  metals  into  groups. 

1 1.  Point  out  the  relations  existing  between  the  oxygen  and 
sulphur  compounds. 

LESSON  XIV.     Silicon,  Boron,  &>c. 

1.  Mention  the  chief  properties  of  selenium  and  tellurium. 

2.  How  is  silicon  prepared  ? 

3.  What  names  does  the  substance  Si  O2  go  by  ? 

4.  How  can  we  obtain  (i)  soluble  and  (2)  insoluble  silica  ? 

5.  How  is  silicic  tetrafluoride  prepared  ? 

6.  Where  does  boracic  acid  occur  ? 

7.  What  is  the  composition  of  borax  ? 


LESSON  XV.    Phosphorus  Compounds. 

1.  Whence  do  animals  ultimately  get  the  phosphorus  which 
they  need  ? 

2.  How  is  phosphorus  prepared  from  bone-ash  ? 

3.  Describe  the  different  modifications  of  phosphorus. 

4.  What  weight  of  phosphorus  pentoxide  can  be  obtained 
by  burning  one  kilo,  of  phosphorus  ? 

5.  How  is  trihydric  phosphate  prepared  ? 


358  Elementary  Chemistry. 

6.  Write  down  the  formulae  of  the  tribasic  sodium  phos 
phates. 

7.  How  many  grms.  of  sodium  metaphosphate  can  be  got 
by  heating  100  grms.  of  microcosmic  salt  ? 

8.  Write  down   the   decomposition  which  occurs  when  we 
mix  solutions  of  hydric  di-sodium  phosphate  and  silver  nitrate 
(Ag  NO,). 

9.  4  (H,  PO3)  =  3  (H3  POO  +  PH3.      Describe   this   de 
composition,   and    give    the    properties    of    the   substances 
formed. 

10.  How  are  the  chlorides  of  phosphorus  prepared  ? 

LESSON  XVI.     Arsenic  Compounds. 

1.  How  is  arsenic  separated  from  its  ores  ? 

2.  Name  the  oxides  of  arsenic.  » 

3.  What  are  the  peculiar  characteristics  of  the  arsenites 
and  arsenates  ? 

4.  How  does  ferric  oxide  act   as  an  antidote  to  the  poi 
sonous  properties  of  the  arsenites  and  arsenates  ? 

5.  What  is  the  composition  and  mode  of  preparation  of 
arseniuretted  hydrogen  ? 

6.  Name  the  tests  by  which  arsenic  can  be  detected  with 
certainty. 

7.  Point  out  the  general  chemical  relations  of  the  arsenic, 
phosphorus,  and  nitrogen  compounds. 

8.  Explain  fully  what  is  meant  when  we  say  that  chlorine 
is  monatomic,  oxygen  is  diatomic,  nitrogen  is  triatomic,  and 
carbon  is  tetratomic. 

9.  Give  examples  of  compound  radicals  belonging  to  the 
monad,  dyad,  and  triad  groups. 

10.  How  is  the  atomicity  of  an  element  or  radical  denoted  ? 

LESSON  XVII.     The  General  Properties  of  the  Metals. 

1.  Name  the  metals  which  are  lighter  than  water. 

2.  At  what  temperature  does  mercury  boil  and  freeze  ? 


Elementary  Chemistry.  359 

3.  Describe  the  modes  in  which  the  metallic  ores  generally 
occur. 

4.  State  some  of  the  peculiar  properties  of  the  alloys. 

5.  Under  what  typical  form  may  all  the  oxides  be  classed  ? 

6.  What  is  meant  by  a  metallic  salt  ? 

7.  To  what  types  do  the  substances  K2  SO4,  Ba  SO4,  Ala 
3SO4,  Ba  N2O6,  AgsPO*,  belong  ? 


LESSON  XVIII.     Crystallography. 

1.  Give  the  chief  characteristics  of  crystalline  structure. 

2.  Distinguish  between  amorphous  and  cellular  structure. 

3.  How  is  the  cube  derived  from  the  regular  octohedron  ? 

4.  Explain  what  is  meant  by  the  axes  of  a  crystal. 

5.  What  are  the  distinguishing  characteristics  of  the  six 
systems  of  crystallography  ? 

6.  How  is  the  rhombohedron  derived  from  the  double  six- 
sided  pyramid  ? 

7.  What  is  the  meaning  of  isomorphous  and  of  dimorphous 

bodies  ? 

LESSON   XIX.     Metals  of  the  Alkalies. 

v  i.  How  was  potassium  first  prepared,  and  how  is  it  now 
manufactured  ?  /         u  v  Q  tf  pit* 

o  2..  State  the  sources  of  the  potassium  compounds.  * 
lf  3.  How  is  caustic  potash  obtained  ?  /£«.  C*+**~  * 

4.  Describe  what  happens  when  gunpowder  is  burnt. 

5.  Supposing  that  the  decomposition  is  a  simple  one,  how 
many  cbc.  of  (i)  carbonic  oxide  and  (2)  of  nitrogen  gas  at  o° 
and  760  mm.  will  be  given  off  by  burning  one  gramme  of 
English  musketry  powder  ? 

6.  Name  the  characteristic  tests  for  potassium  salts. 

7.  What  are  the  sources  of  the  sodium  compounds  ?  - 

8.  Describe  the  salt-cake  process. 

9.  How  many  tons  of  vitriol  containing  72  per  cent,  of  Ha 


360  Elementary  Chemistry. 

SO4  will  be  needed  to  convert  100  tons  of  salt  into  salt-cake, 
and  how  many  tons  of  this  latter  will  be  formed  ? 

10.  How  many  tons  of  aqueous  hydrochloric  acid  contain 
ing  30  per  cent,  of  HC1  will   be  formed  in  the  preceding 
reaction  ? 

1 1.  Describe  the  decompositions  by  which  salt-cake  is  con 
verted  into  soda  ash. 

12.  Required   500  tons  of  soda-crystals,  what  will  be  the 
weight  of  salt  and  pure  sulphuric  acid  needed  ? 

13.  How  were  the  two  new  alkaline  metals  discovered  ? 

14.  Explain   the  analogy  in  constitution  existing  between 
the  potassium  and  ammonium  salts. 

LESSON  XX.      Metals   of  the   Alkaline   Earths   and 
Aluminium. 

1.  What  is  the  composition  of  slaked  lime  ? 

2.  Describe  the  uses  of  lime  in  agriculture. 

3.  How  can  temporarily  hard  water  be  softened  ? 

4.  Name  the  commonest  minerals  containing  barium  and 
strontium. 

5.  How  can  oxygen  gas  be  prepared  from  barium  dioxide, 
and  how  can  this  process  be  rendered  continuous  ? 

6.  Mention  the  distinguishing  reactions  of  the  compounds 
of  calcium,  strontium,  and  barium. 

7.  How  is  metallic  aluminium  prepared  ? 

8.  What  is  the  meaning  of  a  mordant  ? 

9.  Calculate  the  percentage  composition  of  common  alum  ? 

10.  Give  a  short  account  of  the  composition  and  properties 
of  the  different  kinds  of  glass. 

1 1.  How  are  colored  glasses  obtained  ? 

12.  How  is  common  earthenware  glazed  ? 

LESSON  XXI.     Magnesium,  Zinc,  Manganese. 

I.  Find  the  formula  of  a  salt  having  the  following  per 
centage  composition  : 


Elementary  Chemistry.  361 

Magnesium    ....  9-76 

Sulphur I3'oi 

Oxygen 26*01 

\Vater 51-22 

lOO'OO 

2.  How  can  these  magnesium  salts  be  distinguished  and 
separated  from  those  of  calcium  ? 

3.  State  the  method  employed  to  extract  zinc  from  its  ores. 

4.  How  many  grms.  of  crystallized  zinc  sulphate  can  be 
got  from  1,000  grms.  of  blende  ? 

5.  State  the  composition  of  the  several  manganese  oxides. 

6.  How  many  litres  of  oxygen  at  12°  and  under  the  pres 
sure  of  750  mm.  can  be  got  (i)  by  heating  500  grms.  of  man 
ganese  dioxide,  and  (2)  by  treating  the  same  weight  of  the 
same  oxide  with  sulphuric  acid  ? 

7.  What  tests  would  you  employ  to  detect  the  presence  of 
the  compounds  of  zinc,  cadmium,  and  manganese  ? 

LESSON  XXII.    Iron. 

1.  Mention  some  of  the  most  important  physical  properties 
of  iron. 

2.  How  is  ferrous  sulphate  obtained  ?     How  many  tons  of 
crystals  can  be  obtained  by  the  slow  oxidation  of  230  tons  of 
pyrites  containing  37-5  per  cent,  of  sulphur  ? 

3.  What  is  the  composition  of  red  haematite  and  specular 
iron  ore  ? 

4.  How  can  the  ferrous  and  ferric  salts  be  distinguished  ? 

5.  Describe  the  manufacture  of  cast-iron  from  clay  iron 
stone. 

6.  What  chemical  changes  go  on  in  the  processes  of  "  refi 
ning  "  and  "  puddling  ?  " 

7.  How  do  cast-iron,  steel,  and  wrought-iron  differ  in  their 
composition  ? 

8.  Describe  (i)  the  common  method  for  making  steel,  and 
(2)  that  known  as  Bessemer's  method. 

16 


362  Elementary  Chemistry. 

9.  3*285  grms.  of  pure  iron  wire  are  burnt  in  excess  of 
oxygen  and  in  chlorine  gases  ;  required  the  weight  (i)  of 
oxide,  and  (2)  of  chloride  formed. 

10.  What  is  the  cause  of  difference  in  the.  appearance  and 
properties  of  "  mottled  "  and  "  white  "  cast-iron  ? 


LESSON  XXIII.     Cobalt,  Nickel,  Chromium,  Tin,  &c. 

1.  Mention  some  of  the  chemical  characteristics  of  cobalt. 

2.  How  can  cobalt  and  nickel  be  distinguished  by  the  blow 
pipe  ? 

3.  Give  the  formulae  and  names  of  the  chromium  oxides. 

4.  How  can  we  pass  from  chromium  sesquioxide  to  the  tri- 
oxide,  and  vice  versa  ? 

5.  Write  down  the  formulas  of  the  potassium  chromates. 

6.  What  is  the  constitution  and  mode  of  preparation  of 
chlorochromic  oxide  ? 

7.  In  what  form  does  tin  occur  ? 

8.  How  can  tin  compounds  be  distinguished  ? 

9.  What  weight  of  crystallized  "  tin  salts  "  can  be  prepared 
from  one  ton  of  metallic  tin  ? 

LESSON  XXIV.     Antimony,  Lead,  Thallium. 

1.  Write  down  the  formulae  of  the  corresponding  oxides  of 
arsenic  and  antimony. 

2.  How  are  the  two  chlorides  of  antimony  prepared  ? 

3.  How  much  manganese  dioxide,  salt,  and  sulphuric  acid 
will  furnish  chlorine  enough  to  convert  100  grms.  of  antimony 
into  the  trichloride  ? 

4.  Point  out  the  chief  distinguishing  properties  of  the  bis 
muth  compounds. 

5.  Mention  the  decompositions  which  occur  in  the  process 
of  lead  smelting. 

6.  Describe  the  action  of  lead  upon  water. 

7.  How  is  white  lead  manufactured  ? 


Elementary  Chemistry.  363 

8.  ioo  grms.  of  lead  oxide  when  reduced  to  the  metallic 
state  in  a  current  of  hydrogen  lost  7-1724  grms.  Calculate 
the  combining  weight  of  lead. 

9-  4'9975  grms.  of  lead  chloride  needed  3-881  grms.  of 
metallic  silver  for  complete  precipitation.  Required  the 
combining  weight  of  lead,  those  of  silver  and  chlorine  being 
given. 

LESSON  XXV.     Copper  and  the  Noble  Metals. 

1.  How  is  copper  obtained  from  copper  pyrites  ? 

2.  Calculate  the  percentage  of  water  contained  in  crystal 
lized  copper  sulphate. 

3.  What  is  the  density  of  mercury  vapor  ?      Does  it  obey 
the  usual  law  of  densities  ? 

4.  What  weight  of  mercury  and  corrosive  sublimate  must 
be  taken  to  yield  three  kilos,  of  calomel  ? 

5.  How  is  the  silver  extracted  from  argentiferous  lead  ? 

6.  ioo  parts  by  weight  of  silver  yield  132-84  parts  of  silver 
chloride.      Given  the  combining  weight  of  chlorine,  required 
that  of  silver.    /d-u   .'  J  1, 

7.  What  decomposition  does  silver  chloride  undergo  in  the 
light  ? 

8.  Describe  the  method  used  for  the  extraction  of  gold. 

9.  How  can  platinum-ore  be  worked  into  coherent  metal  ? 

10.  Give  the  distinguishing  tests  for  copper,  mercury,  sil 
ver,  and  gold. 

LESSON  XXVI.    Spectrum  Analysis. 

1.  Describe  the  phenomenon  observed  when  a  source  of 
white  light  is  examined  by  means  of  a  prism. 

2.  What  peculiarity  is  observed  in  the  spectra  of  colored 
flames  ? 

3.  How  does  the  spectrum  of  a  glowing  solid  differ  from 
that  of  a  glowing  gas  ? 


364  Elementary  Chemistry. 

4.  Mention  some  facts  to  show  the  extreme  delicacy  of  the 
spectrum  analytical  methods. 

5.  How  can  the  spectra  of  the  metals  be  obtained  ? 

6.  Describe   the   construction  and   mode  of  use  of   the 
spectroscope. 

7.  Explain  what  is  meant  by  Fraunhofer's  lines. 

8.  Describe  shortly  an  experiment  to  show  the  reversion 
of  the  bright  line  of  sodium. 

9.  Why  does   Kirchhoff  conclude  that  iron  exists  in  the 
solar  atmosphere  ? 

10.  How  do  we  know  that  the  fixed  dark  solar  lines  are 
not  caused  by  absorption  in  the  earth's  atmosphere  ? 

11.  How  can  we  learn  the  composition  of  the  atmospheres 
of  the  fixed  stars,  and  why  are  we  in  ignorance  about  the 
composition  of  the  planets  ? 

12.  State  the  results  of  Mr.  Huggins'  observations  upon 
the  spectra  of  the  nebulas. 

LESSON  XXVII.    Introduction  to  Organic  Chemistry. 

1.  Name  the  two  chief  peculiarities  of  the  carbon  com 
pounds. 

2.  Give  examples  of  monad,  dyad,  triad,  and  tetrad  ele 
ments. 

3.  Explain  what  is  meant  by  saturated  and  non-saturated 
carbon  compounds. 

4.  Name  the  chlorine  substitution  products  of  marsh-gas. 

5.  Explain,  with  a  drawing,  the  constitution  of  the  mono-, 
di-,  and  tri-carbon  series  of  saturated  compounds. 

6.  What  is  the  constitution  of  the  hydrides,  chlorides,  and 
alcohols  of  the  first  three  series  of  carbon  compounds  ? 

7.  What  is  meant  by  an  organic  radical,  and  by  the  term 
polyatomic  radicals  ? 

8.  Show  that  the  constitution  of  the  saturated  compound 
benzol,  Cc  H6,  is  different  from  that  of  the  alcohol  group  of 
bodies. 


Elementary  Chemistry.  365 

9.  Give  examples  to  show  the  distinction  between  an  atom 
and  a  molecule. 

to.  How  can  all  chemical  changes  be  represented  as  double 
decompositions  ? 

1  1.  Give  examples  of  bodies  (organic  and  inorganic)  formed 
according  to  the  types  — 


12.  To  what  types  do  the  following  substances  belong: 
magnesium  chloride,  sulphuric  acid,  tribasic  phosphoric 
acid,  nitric  acid,  sulphuretted  hydrogen,  arseniuretted  hydro 
gen  ? 


LESSON  XXVIII.     Organic  Analysis,  &>c. 

[It  will  be  necessary  for  the  pupil  to  work  out  many  more 
exercises  on  the  lesson  than  are  here  given.] 

1.  Describe  shortly  the  process  adopted  for  the  estimation 
of  the  carbon  and  hydrogen  contained  in  organic  compounds. 

2.  0-3059  grm.  of  a  body  containing  carbon,  hydrogen,  and 
oxygen,  yielded  on  combustion  0-6000  grm.  carbonic  acid,  and 
0-3040  grm.  water.     Required  the  relation  between  the  number 
of  atoms  of  the  component  elements. 

3.  What  is  the  molecular  weight  of  an  acid  (mono-chlor- 
acetic)  whose  silver  salt  contains  53*6  per  cent,  of  this  metal  ? 

4.  0-305  grm.  of  an  acid  yielded  on  combustion  0-761  grm. 
of  carbonic  acid  and  0*136  grm.  water  ;  0*391  grm.  of  the  silver 
salt  contained  0-184  grm-  silver.     Required  the  formula  of  the 
acid  containing  carbon,  hydrogen,  and  oxygen. 

5.  How  does  the  determination  of  the  vapor  density  of  an 
organic  body  serve  as  a  means  of  ascertaining  its  molecular 
weight  ? 

6.  What  is  the  density  of  ammonia,  marsh  gas,  olefiant  gas, 
methyl  alcohol,  ethyl  alcohol  ? 


366  Elementary  Chemistry. 

7.  Describe  the  two  methods  employed  for  determination 
of  vapor  density. 

8.  Required  from  the  following  numbers  the  vapor  density 
of  a  hydrocarbon  of  the  marsh  gas  series  : — • 

Globe  filled  with  air        at     i6°'S     7-566  grm. 

vapor    "    140°       7783    " 

Capacity  of  globe  115*5  cbc. 


LESSON  XXIX.     Monatomic  Alcohol  Group. 

i.  Explain  the  analogy  in  constitution  existing  between  the 
ethyl  and  potassium  compounds. 

•2.  Write  down  the  formula  for  ethyl  alcohol,  ether,  acetyl- 
acetate,  aldehyde,  acetamide. 

3.  Give  the  names  of  the  following  : 

TVJ   /f*      TT    \       1  C-jHsO    )  C2Hs   ) 

N(C2H5)4)0  C2H3oU,  C2H6(p. 

C,H.     )  C2H5$ 

4.  What  is  the  chemical  change  which  occurs  in  the  pas 
sage  from  an  alcohol  to  the  corresponding  acid  ? 

5.  Write  down  a  list  of  the  first  eight  alcohols  with  their 
derived  acids. 

6.  Name  the  properties  and  mode  of  preparation  of  methyl 
alcohol. 

7.  What  is    the   action   of   sulphuric    acid  upon   methyl 
alcohol  ? 

8.  By  what  reactions  are  we   enabled  to  pass  from   the 
methyl  to  the  ethyl  series  ? 


LESSON  XXX.     Di-carbon  or  Ethyl  Series. 

1.  How  can  alcohol  be  prepared  from  its  inorganic  ma 
terials  ? 

2.  How  many  grms.  of  alcohol  can  be  completely  burnt  by 
I,ooo  litres  of  oxygen  at  o°  and  760  mm  ? 


Elementary  Chemistry.  367 

3.  Give   the   formulae   for  potassium  ethylate,  potassium- 
ethyl-sulphate,  and  ether. 

4.  Describe  the  continuous  etherification  process. 

5.  Write  down  in   formulae  the  decomposition   by  which 
ethyl  cyanide  yields  propionic  acid. 

6.  How  many  grms.  of  ethylamine  can  be  prepared  from 
loo  of  ethyl-cyanate,  and  how  many  grms.  of  potassium  car 
bonate  will  be  produced  ? 

7.  Write  down  the  formulae  of  propyl  alcohol,  propionic 
acid,  propyl  chloride,  butyl  alcohol. 

8.  How  can  amyl  alcohol  be  prepared  from  C5  Hn  H  ? 

f~*    TT 
Q.  What  is  the  action  of  chlorine  upon  ^  yj11 


10.  How  can  the  higher  alcohols  be  prepared  from  Ameri 
can  petroleum  ? 


LESSON  XXXI.     Compound  Ammonias. 

1.  Mention  the  reactions  by  which  the  compound  alcoholic 
ammonias  can  be  prepared. 

2.  Required  the  percentage  of  platinum  contained  in  2  (N 
(Ca  H5)3  H  Cl)  +  Pt  C14. 

3.  What  is  the  molecular  weight  and  possible  formula  of  a 
double  platinum  salt  yielding  on  heating  29-4  per  cent,  of 
metallic  platinum  ? 

4.  How  is  tetra-ethyl  ammonium  hydrate  prepared  ? 

5.  Give   examples   of   primary,    secondary,    and    tertiary 
monamines. 

6.  How  would  you  determine  the  constitution  of  a  com 
pound  ammonia  of  the  composition  C3  H9  N  ? 

7.  What  is  the  formula  of  tri-ethyl  phosphine,  and  how  is 
this  substance  prepared  ? 

8.  What  is  the  composition  of  cacodyl  and  cacodylic  acid  ? 

9.  How  is   zinc-ethyl  prepared,   and  what  are   its  chief 
properties  ? 


368  Elementary  Chemistry. 

10.  Na  (Ca  H5)  +  CO2  =  C3  H6  Na  O2;   explain  this  re 
action. 

LESSON  XXXII.     Oxidized  Derivatives  of  the  Alcohols. 

1.  Mention  the  chief  reactions  by  which  the  fatty  acids  can 
be  formed. 

2.  How  many  grms.  of  potassium  formate  can  be  got  from 
500  litres  of  carbonic  oxide  at  15°  and  745  mm.  ? 

3.  Required  100  kilos,  of  C  H2  Oa ;  how  many  kilos,  of 
oxalic  acid  are  needed  ? 

4.  What  is  the  formula  of  formamide  ? 

5.  How  can  aldehyde  be  produced  from  acetic  acid,  and 
how  can  aldehyde  be  reduced  to  alcohol  ? 

6.  Explain  what  is  meant  by  the  acetous  fermentation. 

7.  What  is  the  composition  of  red-  and  iron-liquors  ? 

8.  How  many  grms.  of  glacial  acetic  acid  can  be  obtained 
from  25  kilos,  of  potassium  acetate  ? 

9.  How  is  acetyl  acetate  (acetic  anhydride)  prepared  ? 

10.  Name  some  of  the  chlorine  substitution  products  of 
acetic  acid. 

11.  Give  the  formulae  and  mode  of  preparation  of  thiace- 
tic  acid,  acetyl  peroxide,  acetamide,  acetone,  acetylene. 

12.  Show  that  by  substituting  hydrogen  in  the  radical  of 
acetic  acid  by  methyl  and  ethyl  we  obtain  (i)  propionic  and 
(2)  butyric  acids. 

13.  Point  out  several  methods  by  which  we  can  pass  from 
the  di-  to  the  tri-carbon  series. 

LESSON  XXXIII.    Diatomic  Alcohols. 

1.  What  is  meant  by  a  diatomic  alcohol  ? 

2.  Mention  the  chlorine  substitution  products  of  ethylene. 

3.  Why  is  ethylene   regarded    as    a    non-saturated   com 
pound  ? 

/4.  How  is  glycol  prepared  ? 
5.  What  are  the  products  of  oxidation  of  glycol  ? 


Elementary  Chemistry.  369 

6.  How  is  ethylene  oxide  distinguished  from  aldehyde  ? 

7.  How  many  grms.  of  oxygen  are  required  to  burn  com 
pletely  100  grms.  of  tri-ethylene  glycol  ? 

8.  Write  down  a  list  of  the  olifines  with  their  formulae. 

9.  What  is  the  name  of  Ce  ^2  j  O2  ? 

10.  Write  out  the  formulae  of  some  ethylene  di-amines. 


LESSON  XXXIV.     Diatomic  Acids. 

1.  How  are  the  acids  of  (i)  the  lactic  series  and  (2)  those 
of  the  oxalic  series  derived  from  the  corresponding  glycols  ? 

2.  Show  that  hydrated  carbonic  acid  is  the  first  term  of  the 
first  series. 

3.  Write  the  formula  of  di-methyl  sulpho-carbonate. 

4.  How  many  grms.  of  oxygen  are  required  to  oxidize  100 
grms.  of  glycolic  to  oxalic  acid  ? 

5.  Describe  the  manufacture  of  oxalic  acid  from  saw-dust. 

6.  Show  that  lactic  acid  can  be  formed  from  chlor-propionic 
acid. 

7.  In  what  important  respect,  as  regards  the  formation  of 
salts,  do  lactic  acid  and  its  homologues  differ  from  oxalic  acid 
and  the  higher  terms  of  its  series  ? 

8.  How  can  malic  and  tartaric  acid  be  obtained  from  suc- 
cinic  acid  ? 

9.  Describe  the  several  varieties  of  tartaric  acid. 

10.  What  is  the   action   of  hydriodic  acid  upon   tartaric 
acid  ? 

LESSON  XXXV.     Cyanogen  Compounds. 

1.  Write  down  the  typical  formulae  for  the  most  important 
cyanogen  compounds. 

2.  Describe  the  tests  for  hydrocyanic  acid. 

3.  What  are  the  chief  points  of  relationship  between  the 
cyanogen  and  the  oxalic  acid  groups  of  compounds  ? 

1 6* 


370  Elementary  Chemistry. 

4.  How  much  yellow  prussiate  of  potash,  manganese  di 
oxide,  and  ammonium  sulphate  can  yield  500  grms.  urea  ? 

5-  5°  grms'  °f  urine  yielded  on  analysis  475  cbc.  of  nitro 
gen  at  11°  and  754  mm.  Required  the  percentage  of  urea 
contained. 

6.  Write  the  formulae  for  cyanuric  acid,  di-ethyl  urea, 
sulphocyanic  acid,  and  cyanamide. 


LESSON  XXXVI.     Triatomic  and  Hexatomic  Alcohols. 

1.  Show  the  relation  in  composition  existing  between  propyl 
alcohol,  propylene  glycol,  and  glycerine. 

2.  Explain  the  process  of  saponification. 

3.  Explain   by  typical    formula    the   composition  of   the 
chlorhydrines. 

C3H5          \  c\   .  C3  ^5 

4"  (Ci,  H35  O)  H2  \  Ua  >     (C18  H35  O),  H 

C3  H5 

(Ci.  H350)3 
Name  the  above  bodies. 

5.  How  is  allyl  alcohol  prepared  from  glycerine  ? 

6.  What  is  the  composition  of  acroleine  ? 

7.  What  is  the  constitution  of  mannite  ;  and  what  reasons 
have  we  for  supposing  it  to  be  a  hexatomic  alcohol  ? 

8.  How  are  the  so-called  iso-alcohols  prepared  ? 


LESSON  XXXVII.     Sugars  and  Glucoses. 

1.  Give  a  short  description  of  the  preparation  and  refining 
of  cane  sugar. 

2.  Write  down  the  formula  of  sucroses  and  glucoses. 

3.  What  is    meant    by   right-    and    left-handed    rotatory 
power  ? 

4.  What  is  the  action  of  yeast  and  dilute  sulphuric  acid 
upon  cane  sugar  ? 


Elementary  Chemistry.  371 

5.  How  is  dextrose  prepared  ? 

6.  Give  a  short  account  of  the   principal  phenomena  of 
fermentation. 

LESSON  XXXVIII.     Starch,  Gums,  and  Glucosides. 

1.  How  does  starch  differ  in  constitution  from  glucose  ? 

2.  What  weight  of  dextrine  and  dextrose  can  be  obtained 
from  i  kilo,  of  starch  by  the  action  of  diastase  ? 

3.  What  is  the  composition  of  gun  cotton,  and  what  advan- 
tao-es  does  it  offer  over  gunpowder  ? 

4.  C20  H37  N  On  +  2  H20  =  C7  H6  O  4-  HCN  +  2C6  H12 
O6.     Explain  the  above  equation. 

5.  What  is  the  composition  of  ink  ? 

6.  State  some  of  the  general  characteristics  of  a  glucoside. 

LESSON  XXXIX.     Group  of  Aromatic  Compounds. 

1.  How  do   we   suppose  the  carbon  atoms  in  benzol   are 
arranged  ? 

2.  Write  down  the  formulae  for  benzol,  toluol,  xylol,  and 
cumol. 

3.  What  substances  are  formed  by  the  replacement  of  one 
atom  of  hydrogen  in  benzol  by  N  O2,  N  H2  and  HO? 

4.  Describe  the  methods  employed  for  preparing  aniline. 

5.  Required  the  volumes  at  o°  and  760  mm.  of  nitrogen  and 
carbonic  dioxide  obtained  by  the  combustion  of  216  grms.  of 
aniline. 

6.  How  is  rosaniline  prepared  ? 

7.  How  can  oil  of  bitter  almonds  be  converted  into  benzoic 
acid  and  vice  versa  ? 

8.  Explain  the  following  :  — 


9.  Explain  the  relation  of  leucaniline  to  rosaniline,  and  of 
white  to  blue  indigo. 


372  Elementary  Chemistry. 


LESSON  XL.     Turpentines  and  Vegeto-alkaloids. 

1.  What  is  meant  by  physical  isomerism  ? 

2.  What  is  the  general  composition  of  essential  oils  ? 

3.  State   the   composition   and  chief   properties  of  naph- 
thalin. 

4.  What  is  the  chief  coloring  matter  of  madder? 

5.  Name  the  chief   peculiarities  of  the  group  of  vegeto- 
alkaloids. 

6.  What  tests  may  be  used  to  ascertain  the  presence  of 
morphine,  brucine,  and  strychnine  ? 

7.  Point  out  the  chief  properties    of  quinine,  cinchonine, 
and  its  isomers. 

8.  How  is  theobromine  connected  with  theine  ? 

9.  Required  the  molecular  weight  of  an  alkaloid  whose 
hydrochlorate  contains  ii'o  per  cent,  of  chlorine. 

LESSON  XLI.     Albuminous  Substances. 

1.  In  what  chemical  characters  do  the  albuminous  bodies 
differ  from  chemical  compounds  ? 

2.  How  may  fibrin,  albumin,  and  casein  be  separated  ? 

3.  Describe  shortly  the  composition  and  properties  of  blood, 
milk,  and  bile. 

4.  Distinguish  between  animal  and  vegetable  life. 

5.  From  what  source  do  animals  obtain  the  energy  neces 
sary  for  existence,  and  whence  do  plants  draw   the  energy 
needed  for  the  organization  of  their  food  ? 


. 


APPENDIX. 


NOTE. — On  the  Absolute  Weights  of  Hydrogen,  Oxygen^  and  the  other 
Gases. 

IN  the  foregoing  pages  we  have  taken  the  density  of  Oxygen  to  be  16  (Hydrogen  = 
i),  and  we  have  chosen  as  the  standard  of  absolute  weight  Regnault's  number 
i  "429802  as  the  weight  in  grammes  of  i  litre  of  oxygen  gas,  weighed  in  the  latitude 
of  Paris  at  o°  C.,  and  under  a  pressure  of  760  mm.  of  mercury,  this  being  generally 
received  as  the  most  reliable  of  this  great  experimenter's  numbers.  Hence  we 
adopt  --L  of  this,  or  0-0893626,  as  the  absolute  weight  of  i  litre  of  Hydrogen  measured 
under  the  same  circumstances.  Regnault's  experimental  number  for  the  weight  of 
i  litre  of  Hydrogen  is,  however,  0*089578,  and  if  we  accept  both  of  these  experi 
mental  numbers  as  correct,  the  density  of  Oxygen  becomes  15*96  instead  of  16. 

In  his  recent  classical  researches  on  the  combining  weights  of  the  elements  (the 
most  reliable  and  accurate  determinations  which  we  now  possess),  Stas  concludes 
that  the  true  combining  weight,  and  therefore  the  true  density,  of  Oxygen  is  15*960 
when  H  =  i,  and  thus  a  remarkable  confirmation  of  the  accuracy  of  Regnault's 
experimental  results  is  obtained. 

If  we  wish  to  calculate  the  weights  of  the  gases  with  the  greatest  possible  degree 
of  precision,  from  the  best  experimental  data,  we  must  adopt  L^.^U'l.  or  0*089586 
as  the  unit  (or  critK),  and  in  order  to  find  the  weight  of  i  litre  of  the  following  gases, 
or  their  gaseous  compounds,  we  must  multiply  this  number  by  the  densities  of  the 
respective  gases,  as  given  in  (or  obtained  from)  the  accompanying  table,  and  derived 
from  the  combining  weights,  as  determined  by  Stas. 

In  the  third  column  the  experimental  densities  of  the  gases  are  found  as  they  have 
been  determined  by  exact  observation  ;  it  will  be  seen  that  in  some  cases  these  num 
bers  closely  agree  with  those  obtained  by  Stas,  whilst  in  others  (especially  those  of 
the  older  experimenters)  the  difference  becomes  more  apparent. 

i.                      n.  in. 

Density      Weight  of  i  litre  Density 

calculated,  at  o°  &  760  mm.  Experimental. 

(Stas). 

Hydrogen    ....      1*000    .    .    0*089586    .  .  1*000 

Oxygen 15*960    .    .     i '429802    .  .  15*960    Regnault. 

Nitrogen      ....     14*009     .    .     1*255010    .  .  14*025            " 

Chlorine 35'368    .     .     3*168478    .  .  35*343     Bunsen. 

Bromine      ....     79*750     .    .    7*144483    .  .  79*978    Mitscherlich. 

Iodine i26'533     .    .  11*335586     .  .  125*83      Dumas. 

Steam 8*980    .    .    0*804482    .  .  9-001     Gay   Lussac  and 

Thenard. 

Ammonia    ....      8*504    .    .    0*761839    .  .  8*614    Biot  and  Arago. 

Hydrochloric  Acid  .     18*184    .    .     i'62907i    .  .  18*008        "               " 


INDEX. 


\CETAL,  274 

Acetamide,  277 

Acetates  of  the  alkalies,  275 

Acetic  acid,  274 

Acetic  anhydride,  276 

Acetines  or  glycerine  ethers,  304 

Acetone,  277 

Acetous  fermentation,  275,  314 

Acetyl  compounds,  273 

Acetyl  acetate,  276 

Acetyl  benzoate,  326 

Acetyl  chloride,  275 

Acetyl  peroxide,  276 

Acetylene,  277 

Acid,  definition  of,  (note)  66 

Acid  salts,  108 

Acids,  fatty,  group  of,  270 

Acids,  monatomic,  table  of,  249 

Acids  are  hydrogen  salts,  52 

Acraldehyde,  273 

Acroleine,  306 

Acrylic  acid,  306 

Air,  composition  of,  by  weight,  46 

Air,  a  mixture  not  a  compound,  44 

Air,  eudiometric  analysis  of,  44 

Alabaster,  170 

Albumin,  338 

Albuminous  bodies,  composition  of,  339 

Alcohol  (common),  254 

Alcohol  group,  general  re-actions  of,  246 

Alcoholic  fermentation,  314 

Alcohols,  diatomic,  280 

Alcohols,  hexatomic,  307 

Alcohols,  tetratomic,  306 

Alcohols,  triatomic,  301 

Alcaloids,  vegeto,  332 

Aldehyde,  273 

Aldehyde  ammonia,  273 

Alizarine,  331 

Alkaline  earth  metals,  168 

Alkaline  metals,  155 

Allotropic  forms  of  carbon,  65 

Allotropic  forms  of  phosphorus,  127 

Allotropic  forms  of  sulphur,  104 

Alloys  of  the  metals,  146 

Alloys  of  silver,  214 

Allyl  alcohol,  306 


Allyl  ether,  306 

Allyl  sulphide,  306 

Alum  manufacture,  174 

Aluminium,  173 

Amalgams,  147 

Amido-benzol  or  aniline,  322 

Ammonia,  analysis  of,  64 

Ammonia  in  the  air,  49 

Ammonia,  properties  of,  62  * 

Ammonia,  density  of,  27 

Ammonium  theory,  167 

Ammoniacal  salts,  167 

Ammonia  type,  235 

Ammonias,  organic,  264 

Ammonium  cyanate,  299 

Ammonium  nitrate,  64 

Amorphous  structure,  149 

Amorphous  phosphorus,  127 

Amygdaline,  318 

Amyl,  263 

Amyl  alcohol,  261 

Amyl  acetate,  262 

Amyl  ether,  262 

Amyl  hydride,  262 

Amylaceous  bodies  and  gums-,  315 

Analysis  by  volume  of  air,  46 

Anhydrite,  170 

Aniline  or  amido-benzol,  322 

Aniline  blue,  325 

Aniline  colors,  323 

Aniline  colors  obtained  from  coal,  80 

Animal  chemistry,  340 

Animals,  functions  of,  342 

Animal  heat,  343 

Animal  body,  income  and  expenditure 

of,  344 

Anthracite  coal,  composition  of,  69 
Antichlor,  107 

Antimony,  properties  of,  199 
Antimony  compounds,  199 
Antimomuretted  hydrogen,  201 
Antimony  bases,  269 
Aqueous  vapor  in  air,  48 
Aqueous  vapor,  properties  of,  38 
Aromatic  compounds,  319 
Arsenates  of  sodium,  136 
Arsendimethyl,  269 
Arsenic,  133 


376 


Index. 


Arsenic  bases,  268 

Arsenic  tri oxide,  134 

Arsenic  pentoxide,  135 

Arsenic,  tests  for,  137 

Arsenious  acid,  135 

Arseniuretted  hydrogen,  136 

Atmosphere,  the  chemical  composition 

of,  43 

Atomic  theory,  51 

Atomic  and  molecular  formulae,  232 
Atomicity  of  carbon  explained,  229 
Atomicity  of  the  elements,  138 
Atoms,  explanation  of,  51 


B. 

Balling  furnace,  164 

Barium,   172 

Barium  dioxide,  172 

Barium  salts,  173 

Barometer,  construction  of,  25 

Baryta,  172 

Bell-metal,  146 

Benzoic  acid,  326 

Benzoic  alcohol,  325 

Benzoic  aldehyde,  325 

Benzoic  peroxide,  326 

Benzol,  constitution  of,  320 

Benzol,  properties  of,  322 

Benzol,  table  of  derivatives,  320 

Benzoyl  benzoate,  326 

Benzoyl  chloride,  325 

Benzylamine,  327 

Bessemer  steel  process,  190 

Bile,  constituents  of,  341 

Bismuth  compounds,  202 

Bismuth-ethyl,  269 

Bitter  almonds,  318 

Bitter  almonds,  oil  of,  325 

Black-ash  process,  164 

Blast  furnace,  construction  of,  188 

Bleaching  properties  of  chlorine,  87 

Bleaching  powder,  92 

Blende,  103 

Blood  corpuscles,  341 

Blood,  composition  of,  341 

Blowpipe  flame,  nature  of,  82 

Bohemian  glass,  176 

Boiling  points  of  alcohols  and  acids,  249 

Boiling  point,  determination  of,  245 

Boiling  point  of  water,  38 

Bones,  analysis  of,  340 

Boracic  acid,  124 

Borax,  125 

Bor-ethyl,  269 

Boron,  123 

Boyle's  law  of  pressures,  24 

Bromic  acid,  97 

Bromine,  95 

Brown  oil  of  vitriol,  in 


Bronze  and  copper  alloys,  209 

Brucine,  336 

Bunsen's  gas-burner,  82 

Butyl  alcohol,  261 

Butylene,  284 

Butyl  hydride,  260 


C. 

Cacodyl,  269 

Cacodylic  acid,  269 

Cadmium  compounds,  180 

Cassium  compounds,  166 

Caesium  and  rubidium,  discovery  of,  221 

Cafeine,  337 

Calamine,  179 

Calcium,  168 

Calcium  carbonate,  169 

Calcium  oxalate,  290 

Calc  spar,  169 

Calculation  of  vapor  density,  243 

Calculation  of  volumes  of  gases,  25 

Calomel,  or  mercurous  chloride,  212 

Camphors,  328 

Candle,  flame  of,  81 

Cane  sugar,  309 

Cannel  coal,  69 

Cannel  coal  gas,  80 

Caoutchouc,  330 

Carbamide,  or  urea,  299 

Carbon,  properties  of,  65 

Carbon  and  hydrogen,  estimation  of,  236 

Carbon  compounds,  chemistry  of  the,  227 

Carbon,  combining  powers  of,  228 

Carbon  sesqui-chloride,  281 

Carbon  tetra-chloride,  252 

Carbonic  acid,  70 

Carbonic  acid  decomposed  by  sunlight, 

11. 

Carbonic  acid  from  lungs,  1 1,  342 
Carbonic  acid  (hydrated),  286 
Carbonic  acid  in  air,  47 
Carbonic  acid,  synthesis  of,  73 
Carbonic  dioxide,  70 
Carbonic  disulphide,  1 16 
Carbonic  oxide,  formation  of,  75 
Carbonyl  (carbonic  oxide),  288 
Carre's  freezing  machine,  64 
Casein,  339 
Cast  iron,  184 
Caustic  lime,  169 
Caustic  potash,  158 
Caustic  soda,  162 
Cavendish's  apparatus,  29 
Celestine,  171 
Cellulose,  317 
Centigrade  scale,  21 
Cerium,  144 
Cerotyl  alcohol,  264 
Cetyl'alcohol,  263 


Index. 


377 


Chalk,  169 

Charcoal,  properties  of,  68 

Chemical  analysis,  definition  of,  12 

Chemical  balance,  description  of,  3 

Chemical  combination,  examples  of,  i 

Chemical  symbols,  use  and  meaning  of, 
13- 

Chemical  synthesis,  definition  of,  12 

China  clay,  177 

Chinchonas,  alcaloidsof  the,  336 

Chloracetic  acids,  276 

Chloric  acid,  93 

Chlor-carbonyl,  288 

Chlorhydrines  of  glycerine,  303 

Chloral,  274 

Chlorine,  discovery  of,  86 

Chlorine  and  nitrogen,  94 

Chlorine,  oxides  of,  91 

Chlorine,  properties  of,  87 

Chlorine  and  sulphur,  1 16 

Chlorine,  estimations  in  organic  bodies, 

,239 

Chlor-hydro  sulphuric  acid,  113 

Chloro-sulphuric  acid,  113 

Chloroform,  251 

Choke-damp,  nature  of,  71 

Chromates,  194 

Chrome  yellow,  194 

Chromium  compounds,  193 

Cinchonine,  337 

Cinchonidine  and  cinchonicine,  337 

Citric  acid,  294 

Classes  of  metals,  143 

Classification  according  to  types,  233 

Clay,  composition  of,  175 

Clay-iron-stone,  composition  of,  186 

Cleavage  in  crystals,  149 

Coal,  nature  and  composition  of,  69 

Coal  gas,  composition  of,  79 

Cobalt  compounds,  191 

Codeine,  335 

Coefficient  of  expansion  of  gases,  23 

Coke,  79 

Collodion,  318 

Colored  glasses,  176 

Combining  weights  of  the  elements,  6 

Combining  weight,  meaning  of,  13 

Combustion  in  oxygen,  10 

Combustion  of  organic  bodies,  236 

Compound  alcoholic  ammonias,  264 

Compound  gases,  densities  of,  26 

Compounds  of  oxygen  and  nitrogen,  50 

Compound  radicals,  139 

Compound  radicals,  examples  of,  230 

Compound  ureas,  300 

Condy's  liquids,  183 

Conine,  333 

Continuous  spectrum,  220 

Copper,  properties  of,  208 

Copper  salts,  210 

Coral,  composition  of,  71 


Corrosive  sublimate,  212 

Cressol,  321 

Crown  glass,  composition  of,  176 

Crude  wood  spirit,  274 

Cryolite,  top 

Crystallization,  water  of,  149 

Crystallized  phosphorus,  128 

Crystallography,  principles  of,  149 

Crystals  of  leaden  chamber,  1 10 

Cumol,  320 

Cupellation,  process  of,  213 

Cupric  oxide,  209 

Cuprous  oxide,  209 

Cyamilide,  298 

Cyanamide,  301 

Cyanic  acid,  298 

Cyanogen,  properties  of,  84 

Cyanogen  chlorides,  298 

Cyanogen  compounds,  295 

Cyanuric  acid,  300 


D. 

Dalton's  atomic  theory,  51 

Dark  lines  in  solar  spectrum,  223 

Davy  lamp,  83 

Decatyl  hydride,  263 

Decomposition  of  water  by  electricity,  31 

Delicacy  of  spectrum  analysis,  221 

Densities  of  compound  gases,  27 

Density  of  gaseous  elements,  26 

Density  of  vapors,  242 

Density  of  water,  36 

Dew,  formation  of,  49 

Dextrine  or  British  gum,  315 

Dextrose,  311 

Dextro  tartaric  acid,  293 


Diacetine,  304 
Diacetamide,  2 


Diamond,  properties  of,  67 
Diamond  burnt  in  oxygen,  73 
Diamines,  284 
Diatomic  acids,  286 
Diatomic  alcohols,  280 
Diatomic  elements,  139 
Dicarbon  or  ethyl  series,  253 
Dichlorhydrine,  304 
Diethylamine,  265 
Diethyl  glycol,  283 
Diffusion  of  gases,  27 
Di-hydric  sulphate,  109 
Di-hydric  sulphide,  113 
Di-hydric  sulphite,  107 
Dimethyl  acetal,  274 
Dimorphism,  155 
Distilled  water,  40 
Distribution  of  the  elements,  8 
Distribution  of  the  metals,  142 
Dolomite,  178 
Double  decompositions,  53 


373 


Index. 


Earth's  crust,  composition  of,  8 
Earthenware  manufacture,  177 
Ebullition  of  water,  37 
Elastic  force  of  steam,  38 
Electrolysis  of  water,  31 
Elementary  bodies,  list  of,  6 
Elementary  and  compound  substances,  4 
Emerald  green,  135 
Energy  of  animals,  source  of,  343 
Erythrite,  tetratoinic  alcohol,  306 
Essential  oils,  330 
Etching  on  glass,  101 
Etherincation,  process  of,  256 
Ethyl  alcohol,  253 
Ethylamine,  265 

Ethyl  ammonias,  formation  of,  264 
Ethyl  carbonate,  260 
Ethyl  chloride,  258 
Ethyl  compounds,  253 
Ethyl  cyanate,  260 
Ethyl  cyanide,  258 
Ethyl  ether,  252 

Ethyl  group,  general  re-actions  of,  246 
Ethyl  hydride,  259 
Ethyl  nitrate,  259 
Ethyl  oxalate,  290 
Ethyl  phosphates,  260 
Ethyl  sulphide,  259 
Ethylene,  78,  280 
Ethylene  alcohol,  281 
Ethylene  diamines,  284 
Ethylene  dichloride,  281 
Ethylene  oxide,  283 
Ethylines  of  glycerine,  304 
Eudiometric  analysis  of  air,  44 
Eudiometric  synthesis  of  water,  29 
Expansion  of  gases  by  heat,  23 
Exceptions  to  the  law  of  volumes  (note), 
232 

F. 

Fahrenheit's  scale,  22 

Fermentations,  characters  of,  313 

Ferric  acid,  187 

Ferric  salts,  187 

Ferrocyanogen,  297. 

Ferrous  salts,  186 

Fibrin,  339 

Filtration,  process  of,  40. 

Fire-damp  in  coal  mines,  78 

Flame,  nature  of,  81 

Flint  glass,  176 

Flowers  of  sulphur,  104 

Fluorine,  100 

Fluor  spar,  170 

Food  of  plants,  344 

Formamide,  272 

Formic  acid,  272 


Formula,  determination  of,  239 
Fractional  distillation,  245 
Fraunhofer's  lines,  224 
Freezing  machine  with  ammonia,  64 
Freezing  of  water,  34 
Fuel,  composition  of,  69 
Fumaric  acid,  293 
Fusibility  of  metals,  141 

G. 

Galena,  or  lead  sulphide,  205 
Gallic  acid,  319 
Galvanized  zinc,  180 
Gas,  coal  manufacture  of,  79 
Gas  burner,  Bunsen's,  82 
Gases,  calculation  of  volumes  of,  26 
Gases,  expansion  of,  by  heat,  23 
Gases  in  blood,  341 
Gastric  juice,  341 

Gaultheria  procumbens,  oil  of,  327 
Gelatin,  340 
•  General  reactions  for  production  of  fatty 

acids,  271 

Glacial  acetic  acid,  275 
Glass  manufacture,  175 
Glucosides,  group  of,  318 
Glucoses,  312 
Glutin,  339 
Glycerine,  302 
Glycerinic  acid,  303 
Glycerine  ethers,  304 
Glycogen  or  animal  starch,  316 
Glycocine,  327 
Glycol,  281 

Glycol  chlorhydrine,  283 
Glycol  diacetate,  283 
Glycolic  acid,  288 
Glycols,  table  of,  285 
Glyoxal,  282 
Gold  compounds,  217 
Gold,  occurrence  of  metal,  216 
Gold,  malleability  of,  142 
Gramme,  system  of  weights,  20 
Granules  of  starch,  316 
Graphite,  or  plumbago,  67 
Gum  Arabic,  315 
Gun  cotton,  317 
Gun  metal,  146 

Gunpowder,  composition  of,  159 
Guttapercha,  330 
Gypsum,  170 


IT 


Haematin,  coloring  matter  of  blood,  340 
Hail,  formation  of,  48 
Hardness  of  water,  170 
Hartshorn,  spirits  of,  62 


Index. 

Heat,  latent,  of  water,  35  K. 

Heavy  spar,  172 

Heptyl  alcohol,  263  Kaolin,  175 

Hexagonal    system    of  crystallography,  Kirchoff 's  discovery,  224 


379 


Hexatomic  alcohols,  307 

Hexylene,  284 

Hexyl  alcohol,  263 

Higher  alcohols,  263 

Higher  fatty  acids,  278 

Hippuric  acid,  327 

Homologous  series,  245 

Hydraulic  mortar,  169 

Hydric  chloride,  88 

Hydric  ferrocyanide,  297 

Hydric  nitrate,  52 

Hydric  peroxide,  properties  of,  41 

Hydric  persulphide,  115 

Hydriodic  acid,  98 

Hydrobrortlic  acid,  96 

Hydrochloric  acid,  88 

Hydrochloric  acid,  density  of,  27 

Hydrocyanic  acid,  85,  296 

Hydrofluoric  acid,  100 

Hydrogen  production  from  water,  15 

Hydrogen,  properties  of,  14 

Hydrogen,  specific  gravity  of,  17 

Hydrogen  type,  233 

Hydrogen,  weight  of  one  litre  of,  27 

Hygrometers,  49 

Hypobromous  acid,  96 

Hypochlorous  acid,  92. 

Hypochlorous  oxide,  91     • 

Hyposulphites,  113 

Hyposulphurous  acid,  113 


I. 


Illuminating  jxwer  of  coal-gas,  80* 

Indestructibility  of  matter,  3 

Indigo,  328 

Indium,  195 

Ink,  319 

Introduction  to  inorganic  chemistry,  i 

Introduction  to  organic  chemistry,  227 

Inulin,  316 

lodates,  99 

lodic  acid,  99 

Iodine,  97 

Iron  compounds,  185 

Iron  liquor,  275 

Iron  manufacture,  187 

Iron,  properties  of  metallic,  184 

Isatine,  328 

Iso-butyl  iodide,  307 

Iso-hexyl  iodide,  308 

Isomeric  bodies,  281 

Isomorphism,  155 

Iso-propyl  alcohol,  303,  308 


Lactamide,  291 

Lactic  acid,  290 

Lactic  acid,  synthesis  of,  291 

Lactic  fermentation,  315 

Lactic  series  of  acids,  286 

Lactose  or  milk  sugar,  311 

Lactyl  chloride,  291 

Lamp,  safety,  83 

Latent  heat  of  steam,  37 

Latent  heat  of  water,  35 

Laughing  gas,  58 

Lavoisier  on  combustion,  9 

Laws  of  chemical  combination,  50 

Law  of  the  expansion  of  gases,  25,  26 

Lead,  action  of  water  on,  203 

Lead  compounds,  204 

Lead,  metallurgy  of,  202 

Leaden  chamber,  process  of,  1 10 

Leucaniline,  325 

Levro-tartaric  acid,  293 

Levulose,  313 

Light,  action  on  silver  salts,  215 

Light,  action  on  chlorine  and  hydrogen, 

90 

Lime,  169 
Lithium,  166 

Lithium,  occurrence  of,  221 
Litre,  definition  of,  20 
Lixiyiation,  165 
Luminosity  of  flame,  81 
Lunar  caustic,  215 


M. 

Madder,  coloring  matter  of,  331 

Magenta,  324 

Magnesium,  177 

Magnesium  compounds,  178 

Maleic  acid,  293 

Malic  acid,  293 

Malonic  acid,  291 

Manganese  compounds,  181 

Manganese  dioxide,  183 

Manganic  acid,  183 

Mannite,  307 

Mannitic  acid,  313 

Mannite  hexastearate,  308 

Marriotte's  law  of  pressures,  24 

Marsh  gas  or  methyl  hydride,  78, 251 

Mauve,  323 

Measures,  French  system,  18 

Melisyl  alcohol,  264 


Index. 


Melting  points  of  the  metals,  141 

Mercaptan,  259 

Mercuric  cyanide,  297 

Mercury  compounds,  211 

Mercury,  properties  of,  211 

Metaldehyde.  273 

Metallic  chlorides,  148 

Metallic  oxides,  147 

Metallic  salts,  148 

Metallic  sulphides,  147 

Metals,  chemical  properties  of,  146 

Metals,  classification  of,  143 

Metals,  general  properties  of,  140 

Meta-phosphates,  131 

Methylamine,  266 

Methyl  alcohol,  250 

Methyl-benzol  or  toluol,  324 

Methyl  compounds,  250 

Methyl  hydride,  78 

Methyl  oxalate,  290 

Methyl-sulpho  carbonates,  288 

Metre,  length  of  the,  19 

Metric  system  of  measures,  19 

Milk,  composition  of,  342 

Milk  sugar  or  lactose,  311 

Mirror  plate  glass,  176 

Molecular  formulae,  232 

Molecular  weight,  determination  of,  239 

Molecule,  definition  of,  no 

Molybdenum,  198 

Monamines,  table  of,  266 

Monatomic  alcohol  group,  246 

Monatomic  alcohols,  table  of,  249 

Monatomic  elements,  139 

Monatomic  series,  general  re-actions,  278 

Mono-brom-succimc  acid,  292 

Monoclinic  system,  153 

Monocarbon  or  methyl  series,  250 

Mordant  in  calico  printing,  174,  332 

Morphine,  334 

Mortar,  composition  of,  169 

Mucic  acid,  313 

Mucous  fermentation,  315 

Multiple  proportion,  law  of,  50 

Muriatic  acid,  89 


N. 

Naphthalin,  331 
Narcotine,  335 
Nascent  state,  87 
Natural  fats  and  oils,  305 
Nebulae,  spectra  of,  226 
Nickel  compounds,  192 
Nicotine,  333 
Nitre,  158 
Nitric  acid,  54 
Nitric  acid,  tests  for,  55 
Nitric  ether,  259 
Nitric  oxide,  59 


Nitric  pentoxide,  56 

Nitric  peroxide,  61 

Nitric  tetroxide,  61 

Nitric  trioxide,  60 

Nitro-benzol,  322 

Nitro-ferro  cyanides,  298 

Nitro-glycerine,  303 

Nitrogen  determinations,  238 

Nitrogen,  properties  of,  42 

Nitro-manmte,  307 

Nitro-toluol,  324 

Nitrous  anhydride,  60 

Nitrous  ether,  259 

Nitrous  oxide,  £7 

Nordhausen  acid,  109 

Nutrition  of  animals  and  plants,  342 


O. 

Oils  and  fats,  natural,  305 

Oil  of  garlic,  artificial,  306 

Oil  of'mustard,  artificial,  306 

Oil  of  turpentine,  329 

Oil  of  vitriol,  in 

Olefiant  gas,  78,  280 

Olefines,  table  of,  284 

Oleic  acid,  305 

Oleines,  304 

Opium,  alkaloids  of,  334 

Ores,  metallic,  143 

Organic  analysis,  236 

Organic  chemistry,  definition  of,  227 

Organic  compounds,  formulas  of,  239 

Organic  compounds,  synthesis  of,  279 

Organic  matter  in  the  air,  49 

Organizing  action  of  plants,  342 

Orpiment,  137 

Oxalates  of  potassium,  289 

Oxalic  acid,  289 

Oxalic  series  of  acids,  287 

Oxamic  acid,  290 

Oxamide,  290 

Oxidation  products  of  alcohol,  270 

Oxides,  metallic,  147 

Oxygen,  discovery  of,  9 

Oxygen,  modes  of  preparation,  9 

Oxygen  necessary  to  life,  1 1 

Oxygen,  properties  of,  10 

Oxyhydrogen  blowpipe,  34 

Ozone,  nature  pi,  14 

Ozone  in  the  air,  50 


P. 


Palmitic  acid,  264 
Palmitines,  304 
Papaverine,  335 
Paraldehyde,  273 
Paracyanogen,  297 


Index. 


Pearl-ash,  157 

Penta-carbon  series,  261 

Perbromic  acid,  97 

Perchloric  acid,  94 

Periodic  acid,  100 

Permanganates,  183  _ 

Petroleum,  composition  of,  263 

Phosgene  gas,  288 

Phosphates,  constitution  of,  131 

Phosphoric  acids,  131 

Phosphoric  pentoxide,  128 

Phosphoric  trioxide,  128 

Phosphorus,  125 

Phosphorus  bases,  268 

Phosphorus  and  chlorine,  133 

Phosphuretted  hydrogen,  132 

Photography,  use  of  silver  salts  in,  215 

Phthalic  acid,  331 

Physical  properties  of  gases,  18 

Physical  properties  of  sugar,  310 

Physiological   chemistry,    definition    of, 

344 

Piperidine,  333 
Plants,  functions  of,  342 
Platinum  compounds,  218 
Platinum  metals,  rare,  217 
Platinum,  metallurgy  of,  218 
Plumbago,  67 
Polyethylene  glycols,  283 
Polyglycerines,  305 
Porcelain  manufacture,  177 
Potash  caustic,  158 
Potassium,  155 
Potassium  carbonate,  158 
Potassium  chlorate,  12 
Potassium  cyanide,  296 
Potassium  ferricyanide,  298 
Potassium  ferrocyanide,  297 
Potassium  salts,  tests  for,  160 
Potassium,  sources  of,  156 
Pressure,  standard,  26 
Priestley,  discovery  of  oxygen,  9 
Primary  monamines,  266 
Propyl  alcohol,  261 
Prussian  blue,  296 
Prussic  acid,  85 
Puddling  process,  190 
Pyrites  burners,  in 
Pyroligneous  acid,  275 
Pyrophosphates,  130 
Pyrotartaric  acid,  287 


Q. 

Quadratic  system  of  crystals,  151 

)uartz,  120 

jjuick  lime,  169 

Juinjdme  and  quinicine,  337 

juinine,  336 


R. 

Racemic  acid,  293 

Rain,  cause  of,  48 

Reaumur's  scale,  22 

Red  liquor,  275 

Red  lead,  204 

Red  phosphorus,  127 

Refining  process  of  iron,  190 

Refining  of  sugar,  310 

Regular  system  of  crystals,  150 

Relation  of  gases  to  pressure,  24 

Resins  and  balsams,  330 

Respiration  and  animal  heat,  343 

Rhombic  system,  152 

Rock  crystal,  120 

Rock  salt,  161 

Rosaniline,  324 

Rubian,  331 

Rubidium  compounds,  166 


Saccharic  acid,  313 

Saccharine  and  amylaceous  group,  308 

Safety  lamp,  83 

Sal-ammoniac,  62,  168 

Salicine,  318 

Salicylic  group,  327 

Salt  cake  process,  163 

Saltpetre,  158 

Salts  of  the  metals,  148 

Saponification,  process  of,  302,  303 

Saturated  compounds,  definition  of,  228 

Scheele's  green,  135 

Secondary  monamines,  list  of,  267 

Selenic  oxides,  117 

Selenium,  117 

Seleniuretted  hydrogen,  118 

Silica,  120 

Silicic  dioxide,  120 

Silicic  tetrachloride,  122 

Silicic  tetrafluoride,  123 

Silicon,  120 

Silver  compounds,  214 

Silver,  extraction  of,  from  ores,  213 

Soda-ash  process,  164 

Soda  caustic,  162 

Soda-crystals,  165 

Soda  manufacture,  163 

Sodium,  161 

Sodium  carbonate,  162 

Sodium  chloride,  162 

Sodium  ethyl,  270 

Sodium  phosphates,  130 

Sodium  salts,  tests  for,  165 

Solar  chemistry,  223 

Solar  radiations  and  life,  345 

Soluble  starch,  316 

Specific  gravity  of  the  metals,  141 

Spectroscope,  construction  of,  222 


38? 


Index. 


Spectrum  analysis,  219 

Spermaceti,  263 

Sporules  of  ferments,  314  ' 

Standard  gold,  216 

Standard  silver,  214 

Stannic  salts,  196 

Stannous  salts,  196 

Starch,  316 

Steam,  decomposition  of,  15 

Steam,  density  of,  27 

Steam,  elastic  force  of,  39 

Stearines,  304 

Steel,  manufacture  of,  190 

Stellar  chemistry,  226 

Strontium,  171 

Structure  of  flame,  81 

Strychnine,  335 

Strychnos,  alkaloids  of  the,  335 

Substitution  products,  examples  of,  228 

Succinamide,  292 

Succinic  acid,  291 

Succinic  anhydride,  292 

Sucroses,  309 

Sugar  of  lead,  205 

Sugar,  preparation  of,  309 

Sugar,  properties  of,  310 

Sulphates,  constitution  of,  112 

Sulphides,  metallic,  147 

Sulphocarbonic  acid,  288 

Sulphocyanic  acid,  300 

Sulphovinic  acid,  259 

Sulphur,  102 

Sulphur,  preparation  of,  103 

Sulphur  and  oxygen,  105 

Sulphuretted  hydrogen,  1 14 

Sulphuric  acid,  109 

Sulphuric  anhydride,  108 

Sulphuric  dioxide,  105 

Sulphuric  trioxide,  108 

Sulphurous  acid,  105 

Sunlight,  effect  on  plants,  344 

Sun's  atmosphere,  225 

Superphosphate  of  lime,  126 

Symbols  of  the  elements,  6 

Synaptase,  318 

Synthesis  of  alcohol,  250 

Synthesis  of  fatty  acids,  278 

Synthesis  of  monatomic  alcohol  series, 

278 

Synthesis  of  succinic  acid,  292. 
Synthesis  of  water,  31. 
Systems  of  crystallography,  150 


T. 

Table  of  alcohols  and  acids,  249 

Table  of  elements,  6 

Table  of  melting  points,  141 

Table  of  simple  and  mixed  ethers,  257 

Table  of  specific  gravities,  141 


Table  of  weights,  in  appendix,  373 

Tannic  acid,  319 

Tannine,  319 

Tartar  emetic,  294 

Tartaric  acid,  293 

Tartrates,  294 

Taurin,  341 

Taurocholic  acid,  341 

Tellurium,  119 

Temperature,  measurement  of,  20. 

Temperature,  standard,  at  o°  C.,  26 

Tension  of  the  vapor  of  water,  39 

Tertiary  monamines,  list  of,  267 

Tetratomic  alcohols,  306 

Tetra-carbon  series,  261 

Tetra-ethyl  ammonium,  265 

Thallium,  properties  of,  206 

Thebaine,  335 

Theine,  337 

Theobromine,  337 

Thermometers,  construction  of,  21 

Thiacetic  acid,  276 

Tin,  alloys  of,  197 

Tin,  metallurgy  of,  195 

Tin  salts,  196 

Titanium,  198 

Tobacco,  alkaloid  of,  333 

Toluidine,  324 

Toluol  or  methyl-benzol,  324 

Tri-acetine,  304 

Triatomic  alcoho'.s,  301 

Triatomic  elements,  139 

Tricarbon  series,  261 

Tri-chlor-hydrine,  304 

Triclinic  system,  153 

Triethylamine,  265 

Triethyl-phosphine,  268 

Trihydric  phosphate,  129 

Trimethylarsine,  269 

Tri-nitro-glycerine,  303 

Tungsten,  198 

Turnbull's  blue,  298 

Turpentines  and  camphors,  328 

Types,  classification  according  to,  233 

Type  metal,  composition  of,  200 


U. 

Uranium  compounds,  195 
Urea,  compounds  of,  300 
Urea,  synthesis  of,  299 
Uric  acid,  301 

Uric  acid,  derivatives  of,  301 
Urine,  composition  of,  342 


V. 


Valeric  acid,  262 
Vanadium,  198 


Ill 


m 


•RB 


m 


m 


